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30,083 | networkx.classes.graph | has_edge | Returns True if the edge (u, v) is in the graph.
This is the same as `v in G[u]` without KeyError exceptions.
Parameters
----------
u, v : nodes
Nodes can be, for example, strings or numbers.
Nodes must be hashable (and not None) Python objects.
Returns
-------
edge_ind : bool
True if edge is in the graph, False otherwise.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.has_edge(0, 1) # using two nodes
True
>>> e = (0, 1)
>>> G.has_edge(*e) # e is a 2-tuple (u, v)
True
>>> e = (0, 1, {"weight": 7})
>>> G.has_edge(*e[:2]) # e is a 3-tuple (u, v, data_dictionary)
True
The following syntax are equivalent:
>>> G.has_edge(0, 1)
True
>>> 1 in G[0] # though this gives KeyError if 0 not in G
True
| def has_edge(self, u, v):
"""Returns True if the edge (u, v) is in the graph.
This is the same as `v in G[u]` without KeyError exceptions.
Parameters
----------
u, v : nodes
Nodes can be, for example, strings or numbers.
Nodes must be hashable (and not None) Python objects.
Returns
-------
edge_ind : bool
True if edge is in the graph, False otherwise.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.has_edge(0, 1) # using two nodes
True
>>> e = (0, 1)
>>> G.has_edge(*e) # e is a 2-tuple (u, v)
True
>>> e = (0, 1, {"weight": 7})
>>> G.has_edge(*e[:2]) # e is a 3-tuple (u, v, data_dictionary)
True
The following syntax are equivalent:
>>> G.has_edge(0, 1)
True
>>> 1 in G[0] # though this gives KeyError if 0 not in G
True
"""
try:
return v in self._adj[u]
except KeyError:
return False
| (self, u, v) |
30,084 | networkx.classes.graph | has_node | Returns True if the graph contains the node n.
Identical to `n in G`
Parameters
----------
n : node
Examples
--------
>>> G = nx.path_graph(3) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.has_node(0)
True
It is more readable and simpler to use
>>> 0 in G
True
| def has_node(self, n):
"""Returns True if the graph contains the node n.
Identical to `n in G`
Parameters
----------
n : node
Examples
--------
>>> G = nx.path_graph(3) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.has_node(0)
True
It is more readable and simpler to use
>>> 0 in G
True
"""
try:
return n in self._node
except TypeError:
return False
| (self, n) |
30,085 | networkx.classes.digraph | has_predecessor | Returns True if node u has predecessor v.
This is true if graph has the edge u<-v.
| def has_predecessor(self, u, v):
"""Returns True if node u has predecessor v.
This is true if graph has the edge u<-v.
"""
return u in self._pred and v in self._pred[u]
| (self, u, v) |
30,086 | networkx.classes.digraph | has_successor | Returns True if node u has successor v.
This is true if graph has the edge u->v.
| def has_successor(self, u, v):
"""Returns True if node u has successor v.
This is true if graph has the edge u->v.
"""
return u in self._succ and v in self._succ[u]
| (self, u, v) |
30,087 | networkx.classes.digraph | is_directed | Returns True if graph is directed, False otherwise. | def is_directed(self):
"""Returns True if graph is directed, False otherwise."""
return True
| (self) |
30,088 | networkx.classes.digraph | is_multigraph | Returns True if graph is a multigraph, False otherwise. | def is_multigraph(self):
"""Returns True if graph is a multigraph, False otherwise."""
return False
| (self) |
30,089 | networkx.classes.graph | nbunch_iter | Returns an iterator over nodes contained in nbunch that are
also in the graph.
The nodes in nbunch are checked for membership in the graph
and if not are silently ignored.
Parameters
----------
nbunch : single node, container, or all nodes (default= all nodes)
The view will only report edges incident to these nodes.
Returns
-------
niter : iterator
An iterator over nodes in nbunch that are also in the graph.
If nbunch is None, iterate over all nodes in the graph.
Raises
------
NetworkXError
If nbunch is not a node or sequence of nodes.
If a node in nbunch is not hashable.
See Also
--------
Graph.__iter__
Notes
-----
When nbunch is an iterator, the returned iterator yields values
directly from nbunch, becoming exhausted when nbunch is exhausted.
To test whether nbunch is a single node, one can use
"if nbunch in self:", even after processing with this routine.
If nbunch is not a node or a (possibly empty) sequence/iterator
or None, a :exc:`NetworkXError` is raised. Also, if any object in
nbunch is not hashable, a :exc:`NetworkXError` is raised.
| def nbunch_iter(self, nbunch=None):
"""Returns an iterator over nodes contained in nbunch that are
also in the graph.
The nodes in nbunch are checked for membership in the graph
and if not are silently ignored.
Parameters
----------
nbunch : single node, container, or all nodes (default= all nodes)
The view will only report edges incident to these nodes.
Returns
-------
niter : iterator
An iterator over nodes in nbunch that are also in the graph.
If nbunch is None, iterate over all nodes in the graph.
Raises
------
NetworkXError
If nbunch is not a node or sequence of nodes.
If a node in nbunch is not hashable.
See Also
--------
Graph.__iter__
Notes
-----
When nbunch is an iterator, the returned iterator yields values
directly from nbunch, becoming exhausted when nbunch is exhausted.
To test whether nbunch is a single node, one can use
"if nbunch in self:", even after processing with this routine.
If nbunch is not a node or a (possibly empty) sequence/iterator
or None, a :exc:`NetworkXError` is raised. Also, if any object in
nbunch is not hashable, a :exc:`NetworkXError` is raised.
"""
if nbunch is None: # include all nodes via iterator
bunch = iter(self._adj)
elif nbunch in self: # if nbunch is a single node
bunch = iter([nbunch])
else: # if nbunch is a sequence of nodes
def bunch_iter(nlist, adj):
try:
for n in nlist:
if n in adj:
yield n
except TypeError as err:
exc, message = err, err.args[0]
# capture error for non-sequence/iterator nbunch.
if "iter" in message:
exc = NetworkXError(
"nbunch is not a node or a sequence of nodes."
)
# capture error for unhashable node.
if "hashable" in message:
exc = NetworkXError(
f"Node {n} in sequence nbunch is not a valid node."
)
raise exc
bunch = bunch_iter(nbunch, self._adj)
return bunch
| (self, nbunch=None) |
30,090 | networkx.classes.digraph | successors | Returns an iterator over successor nodes of n.
A successor of n is a node m such that there exists a directed
edge from n to m.
Parameters
----------
n : node
A node in the graph
Raises
------
NetworkXError
If n is not in the graph.
See Also
--------
predecessors
Notes
-----
neighbors() and successors() are the same.
| def successors(self, n):
"""Returns an iterator over successor nodes of n.
A successor of n is a node m such that there exists a directed
edge from n to m.
Parameters
----------
n : node
A node in the graph
Raises
------
NetworkXError
If n is not in the graph.
See Also
--------
predecessors
Notes
-----
neighbors() and successors() are the same.
"""
try:
return iter(self._succ[n])
except KeyError as err:
raise NetworkXError(f"The node {n} is not in the digraph.") from err
| (self, n) |
30,091 | networkx.classes.graph | number_of_edges | Returns the number of edges between two nodes.
Parameters
----------
u, v : nodes, optional (default=all edges)
If u and v are specified, return the number of edges between
u and v. Otherwise return the total number of all edges.
Returns
-------
nedges : int
The number of edges in the graph. If nodes `u` and `v` are
specified return the number of edges between those nodes. If
the graph is directed, this only returns the number of edges
from `u` to `v`.
See Also
--------
size
Examples
--------
For undirected graphs, this method counts the total number of
edges in the graph:
>>> G = nx.path_graph(4)
>>> G.number_of_edges()
3
If you specify two nodes, this counts the total number of edges
joining the two nodes:
>>> G.number_of_edges(0, 1)
1
For directed graphs, this method can count the total number of
directed edges from `u` to `v`:
>>> G = nx.DiGraph()
>>> G.add_edge(0, 1)
>>> G.add_edge(1, 0)
>>> G.number_of_edges(0, 1)
1
| def number_of_edges(self, u=None, v=None):
"""Returns the number of edges between two nodes.
Parameters
----------
u, v : nodes, optional (default=all edges)
If u and v are specified, return the number of edges between
u and v. Otherwise return the total number of all edges.
Returns
-------
nedges : int
The number of edges in the graph. If nodes `u` and `v` are
specified return the number of edges between those nodes. If
the graph is directed, this only returns the number of edges
from `u` to `v`.
See Also
--------
size
Examples
--------
For undirected graphs, this method counts the total number of
edges in the graph:
>>> G = nx.path_graph(4)
>>> G.number_of_edges()
3
If you specify two nodes, this counts the total number of edges
joining the two nodes:
>>> G.number_of_edges(0, 1)
1
For directed graphs, this method can count the total number of
directed edges from `u` to `v`:
>>> G = nx.DiGraph()
>>> G.add_edge(0, 1)
>>> G.add_edge(1, 0)
>>> G.number_of_edges(0, 1)
1
"""
if u is None:
return int(self.size())
if v in self._adj[u]:
return 1
return 0
| (self, u=None, v=None) |
30,092 | networkx.classes.graph | number_of_nodes | Returns the number of nodes in the graph.
Returns
-------
nnodes : int
The number of nodes in the graph.
See Also
--------
order: identical method
__len__: identical method
Examples
--------
>>> G = nx.path_graph(3) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.number_of_nodes()
3
| def number_of_nodes(self):
"""Returns the number of nodes in the graph.
Returns
-------
nnodes : int
The number of nodes in the graph.
See Also
--------
order: identical method
__len__: identical method
Examples
--------
>>> G = nx.path_graph(3) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.number_of_nodes()
3
"""
return len(self._node)
| (self) |
30,093 | networkx.classes.graph | order | Returns the number of nodes in the graph.
Returns
-------
nnodes : int
The number of nodes in the graph.
See Also
--------
number_of_nodes: identical method
__len__: identical method
Examples
--------
>>> G = nx.path_graph(3) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.order()
3
| def order(self):
"""Returns the number of nodes in the graph.
Returns
-------
nnodes : int
The number of nodes in the graph.
See Also
--------
number_of_nodes: identical method
__len__: identical method
Examples
--------
>>> G = nx.path_graph(3) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.order()
3
"""
return len(self._node)
| (self) |
30,094 | networkx.classes.digraph | predecessors | Returns an iterator over predecessor nodes of n.
A predecessor of n is a node m such that there exists a directed
edge from m to n.
Parameters
----------
n : node
A node in the graph
Raises
------
NetworkXError
If n is not in the graph.
See Also
--------
successors
| def predecessors(self, n):
"""Returns an iterator over predecessor nodes of n.
A predecessor of n is a node m such that there exists a directed
edge from m to n.
Parameters
----------
n : node
A node in the graph
Raises
------
NetworkXError
If n is not in the graph.
See Also
--------
successors
"""
try:
return iter(self._pred[n])
except KeyError as err:
raise NetworkXError(f"The node {n} is not in the digraph.") from err
| (self, n) |
30,095 | networkx.classes.digraph | remove_edge | Remove the edge between u and v.
Parameters
----------
u, v : nodes
Remove the edge between nodes u and v.
Raises
------
NetworkXError
If there is not an edge between u and v.
See Also
--------
remove_edges_from : remove a collection of edges
Examples
--------
>>> G = nx.Graph() # or DiGraph, etc
>>> nx.add_path(G, [0, 1, 2, 3])
>>> G.remove_edge(0, 1)
>>> e = (1, 2)
>>> G.remove_edge(*e) # unpacks e from an edge tuple
>>> e = (2, 3, {"weight": 7}) # an edge with attribute data
>>> G.remove_edge(*e[:2]) # select first part of edge tuple
| def remove_edge(self, u, v):
"""Remove the edge between u and v.
Parameters
----------
u, v : nodes
Remove the edge between nodes u and v.
Raises
------
NetworkXError
If there is not an edge between u and v.
See Also
--------
remove_edges_from : remove a collection of edges
Examples
--------
>>> G = nx.Graph() # or DiGraph, etc
>>> nx.add_path(G, [0, 1, 2, 3])
>>> G.remove_edge(0, 1)
>>> e = (1, 2)
>>> G.remove_edge(*e) # unpacks e from an edge tuple
>>> e = (2, 3, {"weight": 7}) # an edge with attribute data
>>> G.remove_edge(*e[:2]) # select first part of edge tuple
"""
try:
del self._succ[u][v]
del self._pred[v][u]
except KeyError as err:
raise NetworkXError(f"The edge {u}-{v} not in graph.") from err
nx._clear_cache(self)
| (self, u, v) |
30,096 | networkx.classes.digraph | remove_edges_from | Remove all edges specified in ebunch.
Parameters
----------
ebunch: list or container of edge tuples
Each edge given in the list or container will be removed
from the graph. The edges can be:
- 2-tuples (u, v) edge between u and v.
- 3-tuples (u, v, k) where k is ignored.
See Also
--------
remove_edge : remove a single edge
Notes
-----
Will fail silently if an edge in ebunch is not in the graph.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> ebunch = [(1, 2), (2, 3)]
>>> G.remove_edges_from(ebunch)
| def remove_edges_from(self, ebunch):
"""Remove all edges specified in ebunch.
Parameters
----------
ebunch: list or container of edge tuples
Each edge given in the list or container will be removed
from the graph. The edges can be:
- 2-tuples (u, v) edge between u and v.
- 3-tuples (u, v, k) where k is ignored.
See Also
--------
remove_edge : remove a single edge
Notes
-----
Will fail silently if an edge in ebunch is not in the graph.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> ebunch = [(1, 2), (2, 3)]
>>> G.remove_edges_from(ebunch)
"""
for e in ebunch:
u, v = e[:2] # ignore edge data
if u in self._succ and v in self._succ[u]:
del self._succ[u][v]
del self._pred[v][u]
nx._clear_cache(self)
| (self, ebunch) |
30,097 | networkx.classes.digraph | remove_node | Remove node n.
Removes the node n and all adjacent edges.
Attempting to remove a nonexistent node will raise an exception.
Parameters
----------
n : node
A node in the graph
Raises
------
NetworkXError
If n is not in the graph.
See Also
--------
remove_nodes_from
Examples
--------
>>> G = nx.path_graph(3) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> list(G.edges)
[(0, 1), (1, 2)]
>>> G.remove_node(1)
>>> list(G.edges)
[]
| def remove_node(self, n):
"""Remove node n.
Removes the node n and all adjacent edges.
Attempting to remove a nonexistent node will raise an exception.
Parameters
----------
n : node
A node in the graph
Raises
------
NetworkXError
If n is not in the graph.
See Also
--------
remove_nodes_from
Examples
--------
>>> G = nx.path_graph(3) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> list(G.edges)
[(0, 1), (1, 2)]
>>> G.remove_node(1)
>>> list(G.edges)
[]
"""
try:
nbrs = self._succ[n]
del self._node[n]
except KeyError as err: # NetworkXError if n not in self
raise NetworkXError(f"The node {n} is not in the digraph.") from err
for u in nbrs:
del self._pred[u][n] # remove all edges n-u in digraph
del self._succ[n] # remove node from succ
for u in self._pred[n]:
del self._succ[u][n] # remove all edges n-u in digraph
del self._pred[n] # remove node from pred
nx._clear_cache(self)
| (self, n) |
30,098 | networkx.classes.digraph | remove_nodes_from | Remove multiple nodes.
Parameters
----------
nodes : iterable container
A container of nodes (list, dict, set, etc.). If a node
in the container is not in the graph it is silently ignored.
See Also
--------
remove_node
Notes
-----
When removing nodes from an iterator over the graph you are changing,
a `RuntimeError` will be raised with message:
`RuntimeError: dictionary changed size during iteration`. This
happens when the graph's underlying dictionary is modified during
iteration. To avoid this error, evaluate the iterator into a separate
object, e.g. by using `list(iterator_of_nodes)`, and pass this
object to `G.remove_nodes_from`.
Examples
--------
>>> G = nx.path_graph(3) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> e = list(G.nodes)
>>> e
[0, 1, 2]
>>> G.remove_nodes_from(e)
>>> list(G.nodes)
[]
Evaluate an iterator over a graph if using it to modify the same graph
>>> G = nx.DiGraph([(0, 1), (1, 2), (3, 4)])
>>> # this command will fail, as the graph's dict is modified during iteration
>>> # G.remove_nodes_from(n for n in G.nodes if n < 2)
>>> # this command will work, since the dictionary underlying graph is not modified
>>> G.remove_nodes_from(list(n for n in G.nodes if n < 2))
| def remove_nodes_from(self, nodes):
"""Remove multiple nodes.
Parameters
----------
nodes : iterable container
A container of nodes (list, dict, set, etc.). If a node
in the container is not in the graph it is silently ignored.
See Also
--------
remove_node
Notes
-----
When removing nodes from an iterator over the graph you are changing,
a `RuntimeError` will be raised with message:
`RuntimeError: dictionary changed size during iteration`. This
happens when the graph's underlying dictionary is modified during
iteration. To avoid this error, evaluate the iterator into a separate
object, e.g. by using `list(iterator_of_nodes)`, and pass this
object to `G.remove_nodes_from`.
Examples
--------
>>> G = nx.path_graph(3) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> e = list(G.nodes)
>>> e
[0, 1, 2]
>>> G.remove_nodes_from(e)
>>> list(G.nodes)
[]
Evaluate an iterator over a graph if using it to modify the same graph
>>> G = nx.DiGraph([(0, 1), (1, 2), (3, 4)])
>>> # this command will fail, as the graph's dict is modified during iteration
>>> # G.remove_nodes_from(n for n in G.nodes if n < 2)
>>> # this command will work, since the dictionary underlying graph is not modified
>>> G.remove_nodes_from(list(n for n in G.nodes if n < 2))
"""
for n in nodes:
try:
succs = self._succ[n]
del self._node[n]
for u in succs:
del self._pred[u][n] # remove all edges n-u in digraph
del self._succ[n] # now remove node
for u in self._pred[n]:
del self._succ[u][n] # remove all edges n-u in digraph
del self._pred[n] # now remove node
except KeyError:
pass # silent failure on remove
nx._clear_cache(self)
| (self, nodes) |
30,099 | networkx.classes.digraph | reverse | Returns the reverse of the graph.
The reverse is a graph with the same nodes and edges
but with the directions of the edges reversed.
Parameters
----------
copy : bool optional (default=True)
If True, return a new DiGraph holding the reversed edges.
If False, the reverse graph is created using a view of
the original graph.
| def reverse(self, copy=True):
"""Returns the reverse of the graph.
The reverse is a graph with the same nodes and edges
but with the directions of the edges reversed.
Parameters
----------
copy : bool optional (default=True)
If True, return a new DiGraph holding the reversed edges.
If False, the reverse graph is created using a view of
the original graph.
"""
if copy:
H = self.__class__()
H.graph.update(deepcopy(self.graph))
H.add_nodes_from((n, deepcopy(d)) for n, d in self.nodes.items())
H.add_edges_from((v, u, deepcopy(d)) for u, v, d in self.edges(data=True))
return H
return nx.reverse_view(self)
| (self, copy=True) |
30,100 | networkx.classes.graph | size | Returns the number of edges or total of all edge weights.
Parameters
----------
weight : string or None, optional (default=None)
The edge attribute that holds the numerical value used
as a weight. If None, then each edge has weight 1.
Returns
-------
size : numeric
The number of edges or
(if weight keyword is provided) the total weight sum.
If weight is None, returns an int. Otherwise a float
(or more general numeric if the weights are more general).
See Also
--------
number_of_edges
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.size()
3
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.add_edge("a", "b", weight=2)
>>> G.add_edge("b", "c", weight=4)
>>> G.size()
2
>>> G.size(weight="weight")
6.0
| def size(self, weight=None):
"""Returns the number of edges or total of all edge weights.
Parameters
----------
weight : string or None, optional (default=None)
The edge attribute that holds the numerical value used
as a weight. If None, then each edge has weight 1.
Returns
-------
size : numeric
The number of edges or
(if weight keyword is provided) the total weight sum.
If weight is None, returns an int. Otherwise a float
(or more general numeric if the weights are more general).
See Also
--------
number_of_edges
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.size()
3
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.add_edge("a", "b", weight=2)
>>> G.add_edge("b", "c", weight=4)
>>> G.size()
2
>>> G.size(weight="weight")
6.0
"""
s = sum(d for v, d in self.degree(weight=weight))
# If `weight` is None, the sum of the degrees is guaranteed to be
# even, so we can perform integer division and hence return an
# integer. Otherwise, the sum of the weighted degrees is not
# guaranteed to be an integer, so we perform "real" division.
return s // 2 if weight is None else s / 2
| (self, weight=None) |
30,101 | networkx.classes.graph | subgraph | Returns a SubGraph view of the subgraph induced on `nodes`.
The induced subgraph of the graph contains the nodes in `nodes`
and the edges between those nodes.
Parameters
----------
nodes : list, iterable
A container of nodes which will be iterated through once.
Returns
-------
G : SubGraph View
A subgraph view of the graph. The graph structure cannot be
changed but node/edge attributes can and are shared with the
original graph.
Notes
-----
The graph, edge and node attributes are shared with the original graph.
Changes to the graph structure is ruled out by the view, but changes
to attributes are reflected in the original graph.
To create a subgraph with its own copy of the edge/node attributes use:
G.subgraph(nodes).copy()
For an inplace reduction of a graph to a subgraph you can remove nodes:
G.remove_nodes_from([n for n in G if n not in set(nodes)])
Subgraph views are sometimes NOT what you want. In most cases where
you want to do more than simply look at the induced edges, it makes
more sense to just create the subgraph as its own graph with code like:
::
# Create a subgraph SG based on a (possibly multigraph) G
SG = G.__class__()
SG.add_nodes_from((n, G.nodes[n]) for n in largest_wcc)
if SG.is_multigraph():
SG.add_edges_from(
(n, nbr, key, d)
for n, nbrs in G.adj.items()
if n in largest_wcc
for nbr, keydict in nbrs.items()
if nbr in largest_wcc
for key, d in keydict.items()
)
else:
SG.add_edges_from(
(n, nbr, d)
for n, nbrs in G.adj.items()
if n in largest_wcc
for nbr, d in nbrs.items()
if nbr in largest_wcc
)
SG.graph.update(G.graph)
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> H = G.subgraph([0, 1, 2])
>>> list(H.edges)
[(0, 1), (1, 2)]
| def subgraph(self, nodes):
"""Returns a SubGraph view of the subgraph induced on `nodes`.
The induced subgraph of the graph contains the nodes in `nodes`
and the edges between those nodes.
Parameters
----------
nodes : list, iterable
A container of nodes which will be iterated through once.
Returns
-------
G : SubGraph View
A subgraph view of the graph. The graph structure cannot be
changed but node/edge attributes can and are shared with the
original graph.
Notes
-----
The graph, edge and node attributes are shared with the original graph.
Changes to the graph structure is ruled out by the view, but changes
to attributes are reflected in the original graph.
To create a subgraph with its own copy of the edge/node attributes use:
G.subgraph(nodes).copy()
For an inplace reduction of a graph to a subgraph you can remove nodes:
G.remove_nodes_from([n for n in G if n not in set(nodes)])
Subgraph views are sometimes NOT what you want. In most cases where
you want to do more than simply look at the induced edges, it makes
more sense to just create the subgraph as its own graph with code like:
::
# Create a subgraph SG based on a (possibly multigraph) G
SG = G.__class__()
SG.add_nodes_from((n, G.nodes[n]) for n in largest_wcc)
if SG.is_multigraph():
SG.add_edges_from(
(n, nbr, key, d)
for n, nbrs in G.adj.items()
if n in largest_wcc
for nbr, keydict in nbrs.items()
if nbr in largest_wcc
for key, d in keydict.items()
)
else:
SG.add_edges_from(
(n, nbr, d)
for n, nbrs in G.adj.items()
if n in largest_wcc
for nbr, d in nbrs.items()
if nbr in largest_wcc
)
SG.graph.update(G.graph)
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> H = G.subgraph([0, 1, 2])
>>> list(H.edges)
[(0, 1), (1, 2)]
"""
induced_nodes = nx.filters.show_nodes(self.nbunch_iter(nodes))
# if already a subgraph, don't make a chain
subgraph = nx.subgraph_view
if hasattr(self, "_NODE_OK"):
return subgraph(
self._graph, filter_node=induced_nodes, filter_edge=self._EDGE_OK
)
return subgraph(self, filter_node=induced_nodes)
| (self, nodes) |
30,103 | networkx.classes.graph | to_directed | Returns a directed representation of the graph.
Returns
-------
G : DiGraph
A directed graph with the same name, same nodes, and with
each edge (u, v, data) replaced by two directed edges
(u, v, data) and (v, u, data).
Notes
-----
This returns a "deepcopy" of the edge, node, and
graph attributes which attempts to completely copy
all of the data and references.
This is in contrast to the similar D=DiGraph(G) which returns a
shallow copy of the data.
See the Python copy module for more information on shallow
and deep copies, https://docs.python.org/3/library/copy.html.
Warning: If you have subclassed Graph to use dict-like objects
in the data structure, those changes do not transfer to the
DiGraph created by this method.
Examples
--------
>>> G = nx.Graph() # or MultiGraph, etc
>>> G.add_edge(0, 1)
>>> H = G.to_directed()
>>> list(H.edges)
[(0, 1), (1, 0)]
If already directed, return a (deep) copy
>>> G = nx.DiGraph() # or MultiDiGraph, etc
>>> G.add_edge(0, 1)
>>> H = G.to_directed()
>>> list(H.edges)
[(0, 1)]
| def to_directed(self, as_view=False):
"""Returns a directed representation of the graph.
Returns
-------
G : DiGraph
A directed graph with the same name, same nodes, and with
each edge (u, v, data) replaced by two directed edges
(u, v, data) and (v, u, data).
Notes
-----
This returns a "deepcopy" of the edge, node, and
graph attributes which attempts to completely copy
all of the data and references.
This is in contrast to the similar D=DiGraph(G) which returns a
shallow copy of the data.
See the Python copy module for more information on shallow
and deep copies, https://docs.python.org/3/library/copy.html.
Warning: If you have subclassed Graph to use dict-like objects
in the data structure, those changes do not transfer to the
DiGraph created by this method.
Examples
--------
>>> G = nx.Graph() # or MultiGraph, etc
>>> G.add_edge(0, 1)
>>> H = G.to_directed()
>>> list(H.edges)
[(0, 1), (1, 0)]
If already directed, return a (deep) copy
>>> G = nx.DiGraph() # or MultiDiGraph, etc
>>> G.add_edge(0, 1)
>>> H = G.to_directed()
>>> list(H.edges)
[(0, 1)]
"""
graph_class = self.to_directed_class()
if as_view is True:
return nx.graphviews.generic_graph_view(self, graph_class)
# deepcopy when not a view
G = graph_class()
G.graph.update(deepcopy(self.graph))
G.add_nodes_from((n, deepcopy(d)) for n, d in self._node.items())
G.add_edges_from(
(u, v, deepcopy(data))
for u, nbrs in self._adj.items()
for v, data in nbrs.items()
)
return G
| (self, as_view=False) |
30,104 | networkx.classes.graph | to_directed_class | Returns the class to use for empty directed copies.
If you subclass the base classes, use this to designate
what directed class to use for `to_directed()` copies.
| def to_directed_class(self):
"""Returns the class to use for empty directed copies.
If you subclass the base classes, use this to designate
what directed class to use for `to_directed()` copies.
"""
return nx.DiGraph
| (self) |
30,105 | networkx.classes.digraph | to_undirected | Returns an undirected representation of the digraph.
Parameters
----------
reciprocal : bool (optional)
If True only keep edges that appear in both directions
in the original digraph.
as_view : bool (optional, default=False)
If True return an undirected view of the original directed graph.
Returns
-------
G : Graph
An undirected graph with the same name and nodes and
with edge (u, v, data) if either (u, v, data) or (v, u, data)
is in the digraph. If both edges exist in digraph and
their edge data is different, only one edge is created
with an arbitrary choice of which edge data to use.
You must check and correct for this manually if desired.
See Also
--------
Graph, copy, add_edge, add_edges_from
Notes
-----
If edges in both directions (u, v) and (v, u) exist in the
graph, attributes for the new undirected edge will be a combination of
the attributes of the directed edges. The edge data is updated
in the (arbitrary) order that the edges are encountered. For
more customized control of the edge attributes use add_edge().
This returns a "deepcopy" of the edge, node, and
graph attributes which attempts to completely copy
all of the data and references.
This is in contrast to the similar G=DiGraph(D) which returns a
shallow copy of the data.
See the Python copy module for more information on shallow
and deep copies, https://docs.python.org/3/library/copy.html.
Warning: If you have subclassed DiGraph to use dict-like objects
in the data structure, those changes do not transfer to the
Graph created by this method.
Examples
--------
>>> G = nx.path_graph(2) # or MultiGraph, etc
>>> H = G.to_directed()
>>> list(H.edges)
[(0, 1), (1, 0)]
>>> G2 = H.to_undirected()
>>> list(G2.edges)
[(0, 1)]
| def to_undirected(self, reciprocal=False, as_view=False):
"""Returns an undirected representation of the digraph.
Parameters
----------
reciprocal : bool (optional)
If True only keep edges that appear in both directions
in the original digraph.
as_view : bool (optional, default=False)
If True return an undirected view of the original directed graph.
Returns
-------
G : Graph
An undirected graph with the same name and nodes and
with edge (u, v, data) if either (u, v, data) or (v, u, data)
is in the digraph. If both edges exist in digraph and
their edge data is different, only one edge is created
with an arbitrary choice of which edge data to use.
You must check and correct for this manually if desired.
See Also
--------
Graph, copy, add_edge, add_edges_from
Notes
-----
If edges in both directions (u, v) and (v, u) exist in the
graph, attributes for the new undirected edge will be a combination of
the attributes of the directed edges. The edge data is updated
in the (arbitrary) order that the edges are encountered. For
more customized control of the edge attributes use add_edge().
This returns a "deepcopy" of the edge, node, and
graph attributes which attempts to completely copy
all of the data and references.
This is in contrast to the similar G=DiGraph(D) which returns a
shallow copy of the data.
See the Python copy module for more information on shallow
and deep copies, https://docs.python.org/3/library/copy.html.
Warning: If you have subclassed DiGraph to use dict-like objects
in the data structure, those changes do not transfer to the
Graph created by this method.
Examples
--------
>>> G = nx.path_graph(2) # or MultiGraph, etc
>>> H = G.to_directed()
>>> list(H.edges)
[(0, 1), (1, 0)]
>>> G2 = H.to_undirected()
>>> list(G2.edges)
[(0, 1)]
"""
graph_class = self.to_undirected_class()
if as_view is True:
return nx.graphviews.generic_graph_view(self, graph_class)
# deepcopy when not a view
G = graph_class()
G.graph.update(deepcopy(self.graph))
G.add_nodes_from((n, deepcopy(d)) for n, d in self._node.items())
if reciprocal is True:
G.add_edges_from(
(u, v, deepcopy(d))
for u, nbrs in self._adj.items()
for v, d in nbrs.items()
if v in self._pred[u]
)
else:
G.add_edges_from(
(u, v, deepcopy(d))
for u, nbrs in self._adj.items()
for v, d in nbrs.items()
)
return G
| (self, reciprocal=False, as_view=False) |
30,106 | networkx.classes.graph | to_undirected_class | Returns the class to use for empty undirected copies.
If you subclass the base classes, use this to designate
what directed class to use for `to_directed()` copies.
| def to_undirected_class(self):
"""Returns the class to use for empty undirected copies.
If you subclass the base classes, use this to designate
what directed class to use for `to_directed()` copies.
"""
return Graph
| (self) |
30,107 | networkx.classes.graph | update | Update the graph using nodes/edges/graphs as input.
Like dict.update, this method takes a graph as input, adding the
graph's nodes and edges to this graph. It can also take two inputs:
edges and nodes. Finally it can take either edges or nodes.
To specify only nodes the keyword `nodes` must be used.
The collections of edges and nodes are treated similarly to
the add_edges_from/add_nodes_from methods. When iterated, they
should yield 2-tuples (u, v) or 3-tuples (u, v, datadict).
Parameters
----------
edges : Graph object, collection of edges, or None
The first parameter can be a graph or some edges. If it has
attributes `nodes` and `edges`, then it is taken to be a
Graph-like object and those attributes are used as collections
of nodes and edges to be added to the graph.
If the first parameter does not have those attributes, it is
treated as a collection of edges and added to the graph.
If the first argument is None, no edges are added.
nodes : collection of nodes, or None
The second parameter is treated as a collection of nodes
to be added to the graph unless it is None.
If `edges is None` and `nodes is None` an exception is raised.
If the first parameter is a Graph, then `nodes` is ignored.
Examples
--------
>>> G = nx.path_graph(5)
>>> G.update(nx.complete_graph(range(4, 10)))
>>> from itertools import combinations
>>> edges = (
... (u, v, {"power": u * v})
... for u, v in combinations(range(10, 20), 2)
... if u * v < 225
... )
>>> nodes = [1000] # for singleton, use a container
>>> G.update(edges, nodes)
Notes
-----
It you want to update the graph using an adjacency structure
it is straightforward to obtain the edges/nodes from adjacency.
The following examples provide common cases, your adjacency may
be slightly different and require tweaks of these examples::
>>> # dict-of-set/list/tuple
>>> adj = {1: {2, 3}, 2: {1, 3}, 3: {1, 2}}
>>> e = [(u, v) for u, nbrs in adj.items() for v in nbrs]
>>> G.update(edges=e, nodes=adj)
>>> DG = nx.DiGraph()
>>> # dict-of-dict-of-attribute
>>> adj = {1: {2: 1.3, 3: 0.7}, 2: {1: 1.4}, 3: {1: 0.7}}
>>> e = [(u, v, {"weight": d}) for u, nbrs in adj.items() for v, d in nbrs.items()]
>>> DG.update(edges=e, nodes=adj)
>>> # dict-of-dict-of-dict
>>> adj = {1: {2: {"weight": 1.3}, 3: {"color": 0.7, "weight": 1.2}}}
>>> e = [(u, v, {"weight": d}) for u, nbrs in adj.items() for v, d in nbrs.items()]
>>> DG.update(edges=e, nodes=adj)
>>> # predecessor adjacency (dict-of-set)
>>> pred = {1: {2, 3}, 2: {3}, 3: {3}}
>>> e = [(v, u) for u, nbrs in pred.items() for v in nbrs]
>>> # MultiGraph dict-of-dict-of-dict-of-attribute
>>> MDG = nx.MultiDiGraph()
>>> adj = {
... 1: {2: {0: {"weight": 1.3}, 1: {"weight": 1.2}}},
... 3: {2: {0: {"weight": 0.7}}},
... }
>>> e = [
... (u, v, ekey, d)
... for u, nbrs in adj.items()
... for v, keydict in nbrs.items()
... for ekey, d in keydict.items()
... ]
>>> MDG.update(edges=e)
See Also
--------
add_edges_from: add multiple edges to a graph
add_nodes_from: add multiple nodes to a graph
| def update(self, edges=None, nodes=None):
"""Update the graph using nodes/edges/graphs as input.
Like dict.update, this method takes a graph as input, adding the
graph's nodes and edges to this graph. It can also take two inputs:
edges and nodes. Finally it can take either edges or nodes.
To specify only nodes the keyword `nodes` must be used.
The collections of edges and nodes are treated similarly to
the add_edges_from/add_nodes_from methods. When iterated, they
should yield 2-tuples (u, v) or 3-tuples (u, v, datadict).
Parameters
----------
edges : Graph object, collection of edges, or None
The first parameter can be a graph or some edges. If it has
attributes `nodes` and `edges`, then it is taken to be a
Graph-like object and those attributes are used as collections
of nodes and edges to be added to the graph.
If the first parameter does not have those attributes, it is
treated as a collection of edges and added to the graph.
If the first argument is None, no edges are added.
nodes : collection of nodes, or None
The second parameter is treated as a collection of nodes
to be added to the graph unless it is None.
If `edges is None` and `nodes is None` an exception is raised.
If the first parameter is a Graph, then `nodes` is ignored.
Examples
--------
>>> G = nx.path_graph(5)
>>> G.update(nx.complete_graph(range(4, 10)))
>>> from itertools import combinations
>>> edges = (
... (u, v, {"power": u * v})
... for u, v in combinations(range(10, 20), 2)
... if u * v < 225
... )
>>> nodes = [1000] # for singleton, use a container
>>> G.update(edges, nodes)
Notes
-----
It you want to update the graph using an adjacency structure
it is straightforward to obtain the edges/nodes from adjacency.
The following examples provide common cases, your adjacency may
be slightly different and require tweaks of these examples::
>>> # dict-of-set/list/tuple
>>> adj = {1: {2, 3}, 2: {1, 3}, 3: {1, 2}}
>>> e = [(u, v) for u, nbrs in adj.items() for v in nbrs]
>>> G.update(edges=e, nodes=adj)
>>> DG = nx.DiGraph()
>>> # dict-of-dict-of-attribute
>>> adj = {1: {2: 1.3, 3: 0.7}, 2: {1: 1.4}, 3: {1: 0.7}}
>>> e = [(u, v, {"weight": d}) for u, nbrs in adj.items() for v, d in nbrs.items()]
>>> DG.update(edges=e, nodes=adj)
>>> # dict-of-dict-of-dict
>>> adj = {1: {2: {"weight": 1.3}, 3: {"color": 0.7, "weight": 1.2}}}
>>> e = [(u, v, {"weight": d}) for u, nbrs in adj.items() for v, d in nbrs.items()]
>>> DG.update(edges=e, nodes=adj)
>>> # predecessor adjacency (dict-of-set)
>>> pred = {1: {2, 3}, 2: {3}, 3: {3}}
>>> e = [(v, u) for u, nbrs in pred.items() for v in nbrs]
>>> # MultiGraph dict-of-dict-of-dict-of-attribute
>>> MDG = nx.MultiDiGraph()
>>> adj = {
... 1: {2: {0: {"weight": 1.3}, 1: {"weight": 1.2}}},
... 3: {2: {0: {"weight": 0.7}}},
... }
>>> e = [
... (u, v, ekey, d)
... for u, nbrs in adj.items()
... for v, keydict in nbrs.items()
... for ekey, d in keydict.items()
... ]
>>> MDG.update(edges=e)
See Also
--------
add_edges_from: add multiple edges to a graph
add_nodes_from: add multiple nodes to a graph
"""
if edges is not None:
if nodes is not None:
self.add_nodes_from(nodes)
self.add_edges_from(edges)
else:
# check if edges is a Graph object
try:
graph_nodes = edges.nodes
graph_edges = edges.edges
except AttributeError:
# edge not Graph-like
self.add_edges_from(edges)
else: # edges is Graph-like
self.add_nodes_from(graph_nodes.data())
self.add_edges_from(graph_edges.data())
self.graph.update(edges.graph)
elif nodes is not None:
self.add_nodes_from(nodes)
else:
raise NetworkXError("update needs nodes or edges input")
| (self, edges=None, nodes=None) |
30,108 | networkx.algorithms.tree.mst | EdgePartition |
An enum to store the state of an edge partition. The enum is written to the
edges of a graph before being pasted to `kruskal_mst_edges`. Options are:
- EdgePartition.OPEN
- EdgePartition.INCLUDED
- EdgePartition.EXCLUDED
| class EdgePartition(Enum):
"""
An enum to store the state of an edge partition. The enum is written to the
edges of a graph before being pasted to `kruskal_mst_edges`. Options are:
- EdgePartition.OPEN
- EdgePartition.INCLUDED
- EdgePartition.EXCLUDED
"""
OPEN = 0
INCLUDED = 1
EXCLUDED = 2
| (value, names=None, *, module=None, qualname=None, type=None, start=1) |
30,109 | networkx.exception | ExceededMaxIterations | Raised if a loop iterates too many times without breaking.
This may occur, for example, in an algorithm that computes
progressively better approximations to a value but exceeds an
iteration bound specified by the user.
| class ExceededMaxIterations(NetworkXException):
"""Raised if a loop iterates too many times without breaking.
This may occur, for example, in an algorithm that computes
progressively better approximations to a value but exceeds an
iteration bound specified by the user.
"""
| null |
30,110 | networkx.classes.graph | Graph |
Base class for undirected graphs.
A Graph stores nodes and edges with optional data, or attributes.
Graphs hold undirected edges. Self loops are allowed but multiple
(parallel) edges are not.
Nodes can be arbitrary (hashable) Python objects with optional
key/value attributes, except that `None` is not allowed as a node.
Edges are represented as links between nodes with optional
key/value attributes.
Parameters
----------
incoming_graph_data : input graph (optional, default: None)
Data to initialize graph. If None (default) an empty
graph is created. The data can be any format that is supported
by the to_networkx_graph() function, currently including edge list,
dict of dicts, dict of lists, NetworkX graph, 2D NumPy array, SciPy
sparse matrix, or PyGraphviz graph.
attr : keyword arguments, optional (default= no attributes)
Attributes to add to graph as key=value pairs.
See Also
--------
DiGraph
MultiGraph
MultiDiGraph
Examples
--------
Create an empty graph structure (a "null graph") with no nodes and
no edges.
>>> G = nx.Graph()
G can be grown in several ways.
**Nodes:**
Add one node at a time:
>>> G.add_node(1)
Add the nodes from any container (a list, dict, set or
even the lines from a file or the nodes from another graph).
>>> G.add_nodes_from([2, 3])
>>> G.add_nodes_from(range(100, 110))
>>> H = nx.path_graph(10)
>>> G.add_nodes_from(H)
In addition to strings and integers any hashable Python object
(except None) can represent a node, e.g. a customized node object,
or even another Graph.
>>> G.add_node(H)
**Edges:**
G can also be grown by adding edges.
Add one edge,
>>> G.add_edge(1, 2)
a list of edges,
>>> G.add_edges_from([(1, 2), (1, 3)])
or a collection of edges,
>>> G.add_edges_from(H.edges)
If some edges connect nodes not yet in the graph, the nodes
are added automatically. There are no errors when adding
nodes or edges that already exist.
**Attributes:**
Each graph, node, and edge can hold key/value attribute pairs
in an associated attribute dictionary (the keys must be hashable).
By default these are empty, but can be added or changed using
add_edge, add_node or direct manipulation of the attribute
dictionaries named graph, node and edge respectively.
>>> G = nx.Graph(day="Friday")
>>> G.graph
{'day': 'Friday'}
Add node attributes using add_node(), add_nodes_from() or G.nodes
>>> G.add_node(1, time="5pm")
>>> G.add_nodes_from([3], time="2pm")
>>> G.nodes[1]
{'time': '5pm'}
>>> G.nodes[1]["room"] = 714 # node must exist already to use G.nodes
>>> del G.nodes[1]["room"] # remove attribute
>>> list(G.nodes(data=True))
[(1, {'time': '5pm'}), (3, {'time': '2pm'})]
Add edge attributes using add_edge(), add_edges_from(), subscript
notation, or G.edges.
>>> G.add_edge(1, 2, weight=4.7)
>>> G.add_edges_from([(3, 4), (4, 5)], color="red")
>>> G.add_edges_from([(1, 2, {"color": "blue"}), (2, 3, {"weight": 8})])
>>> G[1][2]["weight"] = 4.7
>>> G.edges[1, 2]["weight"] = 4
Warning: we protect the graph data structure by making `G.edges` a
read-only dict-like structure. However, you can assign to attributes
in e.g. `G.edges[1, 2]`. Thus, use 2 sets of brackets to add/change
data attributes: `G.edges[1, 2]['weight'] = 4`
(For multigraphs: `MG.edges[u, v, key][name] = value`).
**Shortcuts:**
Many common graph features allow python syntax to speed reporting.
>>> 1 in G # check if node in graph
True
>>> [n for n in G if n < 3] # iterate through nodes
[1, 2]
>>> len(G) # number of nodes in graph
5
Often the best way to traverse all edges of a graph is via the neighbors.
The neighbors are reported as an adjacency-dict `G.adj` or `G.adjacency()`
>>> for n, nbrsdict in G.adjacency():
... for nbr, eattr in nbrsdict.items():
... if "weight" in eattr:
... # Do something useful with the edges
... pass
But the edges() method is often more convenient:
>>> for u, v, weight in G.edges.data("weight"):
... if weight is not None:
... # Do something useful with the edges
... pass
**Reporting:**
Simple graph information is obtained using object-attributes and methods.
Reporting typically provides views instead of containers to reduce memory
usage. The views update as the graph is updated similarly to dict-views.
The objects `nodes`, `edges` and `adj` provide access to data attributes
via lookup (e.g. `nodes[n]`, `edges[u, v]`, `adj[u][v]`) and iteration
(e.g. `nodes.items()`, `nodes.data('color')`,
`nodes.data('color', default='blue')` and similarly for `edges`)
Views exist for `nodes`, `edges`, `neighbors()`/`adj` and `degree`.
For details on these and other miscellaneous methods, see below.
**Subclasses (Advanced):**
The Graph class uses a dict-of-dict-of-dict data structure.
The outer dict (node_dict) holds adjacency information keyed by node.
The next dict (adjlist_dict) represents the adjacency information and holds
edge data keyed by neighbor. The inner dict (edge_attr_dict) represents
the edge data and holds edge attribute values keyed by attribute names.
Each of these three dicts can be replaced in a subclass by a user defined
dict-like object. In general, the dict-like features should be
maintained but extra features can be added. To replace one of the
dicts create a new graph class by changing the class(!) variable
holding the factory for that dict-like structure.
node_dict_factory : function, (default: dict)
Factory function to be used to create the dict containing node
attributes, keyed by node id.
It should require no arguments and return a dict-like object
node_attr_dict_factory: function, (default: dict)
Factory function to be used to create the node attribute
dict which holds attribute values keyed by attribute name.
It should require no arguments and return a dict-like object
adjlist_outer_dict_factory : function, (default: dict)
Factory function to be used to create the outer-most dict
in the data structure that holds adjacency info keyed by node.
It should require no arguments and return a dict-like object.
adjlist_inner_dict_factory : function, (default: dict)
Factory function to be used to create the adjacency list
dict which holds edge data keyed by neighbor.
It should require no arguments and return a dict-like object
edge_attr_dict_factory : function, (default: dict)
Factory function to be used to create the edge attribute
dict which holds attribute values keyed by attribute name.
It should require no arguments and return a dict-like object.
graph_attr_dict_factory : function, (default: dict)
Factory function to be used to create the graph attribute
dict which holds attribute values keyed by attribute name.
It should require no arguments and return a dict-like object.
Typically, if your extension doesn't impact the data structure all
methods will inherit without issue except: `to_directed/to_undirected`.
By default these methods create a DiGraph/Graph class and you probably
want them to create your extension of a DiGraph/Graph. To facilitate
this we define two class variables that you can set in your subclass.
to_directed_class : callable, (default: DiGraph or MultiDiGraph)
Class to create a new graph structure in the `to_directed` method.
If `None`, a NetworkX class (DiGraph or MultiDiGraph) is used.
to_undirected_class : callable, (default: Graph or MultiGraph)
Class to create a new graph structure in the `to_undirected` method.
If `None`, a NetworkX class (Graph or MultiGraph) is used.
**Subclassing Example**
Create a low memory graph class that effectively disallows edge
attributes by using a single attribute dict for all edges.
This reduces the memory used, but you lose edge attributes.
>>> class ThinGraph(nx.Graph):
... all_edge_dict = {"weight": 1}
...
... def single_edge_dict(self):
... return self.all_edge_dict
...
... edge_attr_dict_factory = single_edge_dict
>>> G = ThinGraph()
>>> G.add_edge(2, 1)
>>> G[2][1]
{'weight': 1}
>>> G.add_edge(2, 2)
>>> G[2][1] is G[2][2]
True
| class Graph:
"""
Base class for undirected graphs.
A Graph stores nodes and edges with optional data, or attributes.
Graphs hold undirected edges. Self loops are allowed but multiple
(parallel) edges are not.
Nodes can be arbitrary (hashable) Python objects with optional
key/value attributes, except that `None` is not allowed as a node.
Edges are represented as links between nodes with optional
key/value attributes.
Parameters
----------
incoming_graph_data : input graph (optional, default: None)
Data to initialize graph. If None (default) an empty
graph is created. The data can be any format that is supported
by the to_networkx_graph() function, currently including edge list,
dict of dicts, dict of lists, NetworkX graph, 2D NumPy array, SciPy
sparse matrix, or PyGraphviz graph.
attr : keyword arguments, optional (default= no attributes)
Attributes to add to graph as key=value pairs.
See Also
--------
DiGraph
MultiGraph
MultiDiGraph
Examples
--------
Create an empty graph structure (a "null graph") with no nodes and
no edges.
>>> G = nx.Graph()
G can be grown in several ways.
**Nodes:**
Add one node at a time:
>>> G.add_node(1)
Add the nodes from any container (a list, dict, set or
even the lines from a file or the nodes from another graph).
>>> G.add_nodes_from([2, 3])
>>> G.add_nodes_from(range(100, 110))
>>> H = nx.path_graph(10)
>>> G.add_nodes_from(H)
In addition to strings and integers any hashable Python object
(except None) can represent a node, e.g. a customized node object,
or even another Graph.
>>> G.add_node(H)
**Edges:**
G can also be grown by adding edges.
Add one edge,
>>> G.add_edge(1, 2)
a list of edges,
>>> G.add_edges_from([(1, 2), (1, 3)])
or a collection of edges,
>>> G.add_edges_from(H.edges)
If some edges connect nodes not yet in the graph, the nodes
are added automatically. There are no errors when adding
nodes or edges that already exist.
**Attributes:**
Each graph, node, and edge can hold key/value attribute pairs
in an associated attribute dictionary (the keys must be hashable).
By default these are empty, but can be added or changed using
add_edge, add_node or direct manipulation of the attribute
dictionaries named graph, node and edge respectively.
>>> G = nx.Graph(day="Friday")
>>> G.graph
{'day': 'Friday'}
Add node attributes using add_node(), add_nodes_from() or G.nodes
>>> G.add_node(1, time="5pm")
>>> G.add_nodes_from([3], time="2pm")
>>> G.nodes[1]
{'time': '5pm'}
>>> G.nodes[1]["room"] = 714 # node must exist already to use G.nodes
>>> del G.nodes[1]["room"] # remove attribute
>>> list(G.nodes(data=True))
[(1, {'time': '5pm'}), (3, {'time': '2pm'})]
Add edge attributes using add_edge(), add_edges_from(), subscript
notation, or G.edges.
>>> G.add_edge(1, 2, weight=4.7)
>>> G.add_edges_from([(3, 4), (4, 5)], color="red")
>>> G.add_edges_from([(1, 2, {"color": "blue"}), (2, 3, {"weight": 8})])
>>> G[1][2]["weight"] = 4.7
>>> G.edges[1, 2]["weight"] = 4
Warning: we protect the graph data structure by making `G.edges` a
read-only dict-like structure. However, you can assign to attributes
in e.g. `G.edges[1, 2]`. Thus, use 2 sets of brackets to add/change
data attributes: `G.edges[1, 2]['weight'] = 4`
(For multigraphs: `MG.edges[u, v, key][name] = value`).
**Shortcuts:**
Many common graph features allow python syntax to speed reporting.
>>> 1 in G # check if node in graph
True
>>> [n for n in G if n < 3] # iterate through nodes
[1, 2]
>>> len(G) # number of nodes in graph
5
Often the best way to traverse all edges of a graph is via the neighbors.
The neighbors are reported as an adjacency-dict `G.adj` or `G.adjacency()`
>>> for n, nbrsdict in G.adjacency():
... for nbr, eattr in nbrsdict.items():
... if "weight" in eattr:
... # Do something useful with the edges
... pass
But the edges() method is often more convenient:
>>> for u, v, weight in G.edges.data("weight"):
... if weight is not None:
... # Do something useful with the edges
... pass
**Reporting:**
Simple graph information is obtained using object-attributes and methods.
Reporting typically provides views instead of containers to reduce memory
usage. The views update as the graph is updated similarly to dict-views.
The objects `nodes`, `edges` and `adj` provide access to data attributes
via lookup (e.g. `nodes[n]`, `edges[u, v]`, `adj[u][v]`) and iteration
(e.g. `nodes.items()`, `nodes.data('color')`,
`nodes.data('color', default='blue')` and similarly for `edges`)
Views exist for `nodes`, `edges`, `neighbors()`/`adj` and `degree`.
For details on these and other miscellaneous methods, see below.
**Subclasses (Advanced):**
The Graph class uses a dict-of-dict-of-dict data structure.
The outer dict (node_dict) holds adjacency information keyed by node.
The next dict (adjlist_dict) represents the adjacency information and holds
edge data keyed by neighbor. The inner dict (edge_attr_dict) represents
the edge data and holds edge attribute values keyed by attribute names.
Each of these three dicts can be replaced in a subclass by a user defined
dict-like object. In general, the dict-like features should be
maintained but extra features can be added. To replace one of the
dicts create a new graph class by changing the class(!) variable
holding the factory for that dict-like structure.
node_dict_factory : function, (default: dict)
Factory function to be used to create the dict containing node
attributes, keyed by node id.
It should require no arguments and return a dict-like object
node_attr_dict_factory: function, (default: dict)
Factory function to be used to create the node attribute
dict which holds attribute values keyed by attribute name.
It should require no arguments and return a dict-like object
adjlist_outer_dict_factory : function, (default: dict)
Factory function to be used to create the outer-most dict
in the data structure that holds adjacency info keyed by node.
It should require no arguments and return a dict-like object.
adjlist_inner_dict_factory : function, (default: dict)
Factory function to be used to create the adjacency list
dict which holds edge data keyed by neighbor.
It should require no arguments and return a dict-like object
edge_attr_dict_factory : function, (default: dict)
Factory function to be used to create the edge attribute
dict which holds attribute values keyed by attribute name.
It should require no arguments and return a dict-like object.
graph_attr_dict_factory : function, (default: dict)
Factory function to be used to create the graph attribute
dict which holds attribute values keyed by attribute name.
It should require no arguments and return a dict-like object.
Typically, if your extension doesn't impact the data structure all
methods will inherit without issue except: `to_directed/to_undirected`.
By default these methods create a DiGraph/Graph class and you probably
want them to create your extension of a DiGraph/Graph. To facilitate
this we define two class variables that you can set in your subclass.
to_directed_class : callable, (default: DiGraph or MultiDiGraph)
Class to create a new graph structure in the `to_directed` method.
If `None`, a NetworkX class (DiGraph or MultiDiGraph) is used.
to_undirected_class : callable, (default: Graph or MultiGraph)
Class to create a new graph structure in the `to_undirected` method.
If `None`, a NetworkX class (Graph or MultiGraph) is used.
**Subclassing Example**
Create a low memory graph class that effectively disallows edge
attributes by using a single attribute dict for all edges.
This reduces the memory used, but you lose edge attributes.
>>> class ThinGraph(nx.Graph):
... all_edge_dict = {"weight": 1}
...
... def single_edge_dict(self):
... return self.all_edge_dict
...
... edge_attr_dict_factory = single_edge_dict
>>> G = ThinGraph()
>>> G.add_edge(2, 1)
>>> G[2][1]
{'weight': 1}
>>> G.add_edge(2, 2)
>>> G[2][1] is G[2][2]
True
"""
_adj = _CachedPropertyResetterAdj()
_node = _CachedPropertyResetterNode()
node_dict_factory = dict
node_attr_dict_factory = dict
adjlist_outer_dict_factory = dict
adjlist_inner_dict_factory = dict
edge_attr_dict_factory = dict
graph_attr_dict_factory = dict
def to_directed_class(self):
"""Returns the class to use for empty directed copies.
If you subclass the base classes, use this to designate
what directed class to use for `to_directed()` copies.
"""
return nx.DiGraph
def to_undirected_class(self):
"""Returns the class to use for empty undirected copies.
If you subclass the base classes, use this to designate
what directed class to use for `to_directed()` copies.
"""
return Graph
def __init__(self, incoming_graph_data=None, **attr):
"""Initialize a graph with edges, name, or graph attributes.
Parameters
----------
incoming_graph_data : input graph (optional, default: None)
Data to initialize graph. If None (default) an empty
graph is created. The data can be an edge list, or any
NetworkX graph object. If the corresponding optional Python
packages are installed the data can also be a 2D NumPy array, a
SciPy sparse array, or a PyGraphviz graph.
attr : keyword arguments, optional (default= no attributes)
Attributes to add to graph as key=value pairs.
See Also
--------
convert
Examples
--------
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G = nx.Graph(name="my graph")
>>> e = [(1, 2), (2, 3), (3, 4)] # list of edges
>>> G = nx.Graph(e)
Arbitrary graph attribute pairs (key=value) may be assigned
>>> G = nx.Graph(e, day="Friday")
>>> G.graph
{'day': 'Friday'}
"""
self.graph = self.graph_attr_dict_factory() # dictionary for graph attributes
self._node = self.node_dict_factory() # empty node attribute dict
self._adj = self.adjlist_outer_dict_factory() # empty adjacency dict
self.__networkx_cache__ = {}
# attempt to load graph with data
if incoming_graph_data is not None:
convert.to_networkx_graph(incoming_graph_data, create_using=self)
# load graph attributes (must be after convert)
self.graph.update(attr)
@cached_property
def adj(self):
"""Graph adjacency object holding the neighbors of each node.
This object is a read-only dict-like structure with node keys
and neighbor-dict values. The neighbor-dict is keyed by neighbor
to the edge-data-dict. So `G.adj[3][2]['color'] = 'blue'` sets
the color of the edge `(3, 2)` to `"blue"`.
Iterating over G.adj behaves like a dict. Useful idioms include
`for nbr, datadict in G.adj[n].items():`.
The neighbor information is also provided by subscripting the graph.
So `for nbr, foovalue in G[node].data('foo', default=1):` works.
For directed graphs, `G.adj` holds outgoing (successor) info.
"""
return AdjacencyView(self._adj)
@property
def name(self):
"""String identifier of the graph.
This graph attribute appears in the attribute dict G.graph
keyed by the string `"name"`. as well as an attribute (technically
a property) `G.name`. This is entirely user controlled.
"""
return self.graph.get("name", "")
@name.setter
def name(self, s):
self.graph["name"] = s
nx._clear_cache(self)
def __str__(self):
"""Returns a short summary of the graph.
Returns
-------
info : string
Graph information including the graph name (if any), graph type, and the
number of nodes and edges.
Examples
--------
>>> G = nx.Graph(name="foo")
>>> str(G)
"Graph named 'foo' with 0 nodes and 0 edges"
>>> G = nx.path_graph(3)
>>> str(G)
'Graph with 3 nodes and 2 edges'
"""
return "".join(
[
type(self).__name__,
f" named {self.name!r}" if self.name else "",
f" with {self.number_of_nodes()} nodes and {self.number_of_edges()} edges",
]
)
def __iter__(self):
"""Iterate over the nodes. Use: 'for n in G'.
Returns
-------
niter : iterator
An iterator over all nodes in the graph.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> [n for n in G]
[0, 1, 2, 3]
>>> list(G)
[0, 1, 2, 3]
"""
return iter(self._node)
def __contains__(self, n):
"""Returns True if n is a node, False otherwise. Use: 'n in G'.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> 1 in G
True
"""
try:
return n in self._node
except TypeError:
return False
def __len__(self):
"""Returns the number of nodes in the graph. Use: 'len(G)'.
Returns
-------
nnodes : int
The number of nodes in the graph.
See Also
--------
number_of_nodes: identical method
order: identical method
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> len(G)
4
"""
return len(self._node)
def __getitem__(self, n):
"""Returns a dict of neighbors of node n. Use: 'G[n]'.
Parameters
----------
n : node
A node in the graph.
Returns
-------
adj_dict : dictionary
The adjacency dictionary for nodes connected to n.
Notes
-----
G[n] is the same as G.adj[n] and similar to G.neighbors(n)
(which is an iterator over G.adj[n])
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G[0]
AtlasView({1: {}})
"""
return self.adj[n]
def add_node(self, node_for_adding, **attr):
"""Add a single node `node_for_adding` and update node attributes.
Parameters
----------
node_for_adding : node
A node can be any hashable Python object except None.
attr : keyword arguments, optional
Set or change node attributes using key=value.
See Also
--------
add_nodes_from
Examples
--------
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.add_node(1)
>>> G.add_node("Hello")
>>> K3 = nx.Graph([(0, 1), (1, 2), (2, 0)])
>>> G.add_node(K3)
>>> G.number_of_nodes()
3
Use keywords set/change node attributes:
>>> G.add_node(1, size=10)
>>> G.add_node(3, weight=0.4, UTM=("13S", 382871, 3972649))
Notes
-----
A hashable object is one that can be used as a key in a Python
dictionary. This includes strings, numbers, tuples of strings
and numbers, etc.
On many platforms hashable items also include mutables such as
NetworkX Graphs, though one should be careful that the hash
doesn't change on mutables.
"""
if node_for_adding not in self._node:
if node_for_adding is None:
raise ValueError("None cannot be a node")
self._adj[node_for_adding] = self.adjlist_inner_dict_factory()
attr_dict = self._node[node_for_adding] = self.node_attr_dict_factory()
attr_dict.update(attr)
else: # update attr even if node already exists
self._node[node_for_adding].update(attr)
nx._clear_cache(self)
def add_nodes_from(self, nodes_for_adding, **attr):
"""Add multiple nodes.
Parameters
----------
nodes_for_adding : iterable container
A container of nodes (list, dict, set, etc.).
OR
A container of (node, attribute dict) tuples.
Node attributes are updated using the attribute dict.
attr : keyword arguments, optional (default= no attributes)
Update attributes for all nodes in nodes.
Node attributes specified in nodes as a tuple take
precedence over attributes specified via keyword arguments.
See Also
--------
add_node
Notes
-----
When adding nodes from an iterator over the graph you are changing,
a `RuntimeError` can be raised with message:
`RuntimeError: dictionary changed size during iteration`. This
happens when the graph's underlying dictionary is modified during
iteration. To avoid this error, evaluate the iterator into a separate
object, e.g. by using `list(iterator_of_nodes)`, and pass this
object to `G.add_nodes_from`.
Examples
--------
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.add_nodes_from("Hello")
>>> K3 = nx.Graph([(0, 1), (1, 2), (2, 0)])
>>> G.add_nodes_from(K3)
>>> sorted(G.nodes(), key=str)
[0, 1, 2, 'H', 'e', 'l', 'o']
Use keywords to update specific node attributes for every node.
>>> G.add_nodes_from([1, 2], size=10)
>>> G.add_nodes_from([3, 4], weight=0.4)
Use (node, attrdict) tuples to update attributes for specific nodes.
>>> G.add_nodes_from([(1, dict(size=11)), (2, {"color": "blue"})])
>>> G.nodes[1]["size"]
11
>>> H = nx.Graph()
>>> H.add_nodes_from(G.nodes(data=True))
>>> H.nodes[1]["size"]
11
Evaluate an iterator over a graph if using it to modify the same graph
>>> G = nx.Graph([(0, 1), (1, 2), (3, 4)])
>>> # wrong way - will raise RuntimeError
>>> # G.add_nodes_from(n + 1 for n in G.nodes)
>>> # correct way
>>> G.add_nodes_from(list(n + 1 for n in G.nodes))
"""
for n in nodes_for_adding:
try:
newnode = n not in self._node
newdict = attr
except TypeError:
n, ndict = n
newnode = n not in self._node
newdict = attr.copy()
newdict.update(ndict)
if newnode:
if n is None:
raise ValueError("None cannot be a node")
self._adj[n] = self.adjlist_inner_dict_factory()
self._node[n] = self.node_attr_dict_factory()
self._node[n].update(newdict)
nx._clear_cache(self)
def remove_node(self, n):
"""Remove node n.
Removes the node n and all adjacent edges.
Attempting to remove a nonexistent node will raise an exception.
Parameters
----------
n : node
A node in the graph
Raises
------
NetworkXError
If n is not in the graph.
See Also
--------
remove_nodes_from
Examples
--------
>>> G = nx.path_graph(3) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> list(G.edges)
[(0, 1), (1, 2)]
>>> G.remove_node(1)
>>> list(G.edges)
[]
"""
adj = self._adj
try:
nbrs = list(adj[n]) # list handles self-loops (allows mutation)
del self._node[n]
except KeyError as err: # NetworkXError if n not in self
raise NetworkXError(f"The node {n} is not in the graph.") from err
for u in nbrs:
del adj[u][n] # remove all edges n-u in graph
del adj[n] # now remove node
nx._clear_cache(self)
def remove_nodes_from(self, nodes):
"""Remove multiple nodes.
Parameters
----------
nodes : iterable container
A container of nodes (list, dict, set, etc.). If a node
in the container is not in the graph it is silently
ignored.
See Also
--------
remove_node
Notes
-----
When removing nodes from an iterator over the graph you are changing,
a `RuntimeError` will be raised with message:
`RuntimeError: dictionary changed size during iteration`. This
happens when the graph's underlying dictionary is modified during
iteration. To avoid this error, evaluate the iterator into a separate
object, e.g. by using `list(iterator_of_nodes)`, and pass this
object to `G.remove_nodes_from`.
Examples
--------
>>> G = nx.path_graph(3) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> e = list(G.nodes)
>>> e
[0, 1, 2]
>>> G.remove_nodes_from(e)
>>> list(G.nodes)
[]
Evaluate an iterator over a graph if using it to modify the same graph
>>> G = nx.Graph([(0, 1), (1, 2), (3, 4)])
>>> # this command will fail, as the graph's dict is modified during iteration
>>> # G.remove_nodes_from(n for n in G.nodes if n < 2)
>>> # this command will work, since the dictionary underlying graph is not modified
>>> G.remove_nodes_from(list(n for n in G.nodes if n < 2))
"""
adj = self._adj
for n in nodes:
try:
del self._node[n]
for u in list(adj[n]): # list handles self-loops
del adj[u][n] # (allows mutation of dict in loop)
del adj[n]
except KeyError:
pass
nx._clear_cache(self)
@cached_property
def nodes(self):
"""A NodeView of the Graph as G.nodes or G.nodes().
Can be used as `G.nodes` for data lookup and for set-like operations.
Can also be used as `G.nodes(data='color', default=None)` to return a
NodeDataView which reports specific node data but no set operations.
It presents a dict-like interface as well with `G.nodes.items()`
iterating over `(node, nodedata)` 2-tuples and `G.nodes[3]['foo']`
providing the value of the `foo` attribute for node `3`. In addition,
a view `G.nodes.data('foo')` provides a dict-like interface to the
`foo` attribute of each node. `G.nodes.data('foo', default=1)`
provides a default for nodes that do not have attribute `foo`.
Parameters
----------
data : string or bool, optional (default=False)
The node attribute returned in 2-tuple (n, ddict[data]).
If True, return entire node attribute dict as (n, ddict).
If False, return just the nodes n.
default : value, optional (default=None)
Value used for nodes that don't have the requested attribute.
Only relevant if data is not True or False.
Returns
-------
NodeView
Allows set-like operations over the nodes as well as node
attribute dict lookup and calling to get a NodeDataView.
A NodeDataView iterates over `(n, data)` and has no set operations.
A NodeView iterates over `n` and includes set operations.
When called, if data is False, an iterator over nodes.
Otherwise an iterator of 2-tuples (node, attribute value)
where the attribute is specified in `data`.
If data is True then the attribute becomes the
entire data dictionary.
Notes
-----
If your node data is not needed, it is simpler and equivalent
to use the expression ``for n in G``, or ``list(G)``.
Examples
--------
There are two simple ways of getting a list of all nodes in the graph:
>>> G = nx.path_graph(3)
>>> list(G.nodes)
[0, 1, 2]
>>> list(G)
[0, 1, 2]
To get the node data along with the nodes:
>>> G.add_node(1, time="5pm")
>>> G.nodes[0]["foo"] = "bar"
>>> list(G.nodes(data=True))
[(0, {'foo': 'bar'}), (1, {'time': '5pm'}), (2, {})]
>>> list(G.nodes.data())
[(0, {'foo': 'bar'}), (1, {'time': '5pm'}), (2, {})]
>>> list(G.nodes(data="foo"))
[(0, 'bar'), (1, None), (2, None)]
>>> list(G.nodes.data("foo"))
[(0, 'bar'), (1, None), (2, None)]
>>> list(G.nodes(data="time"))
[(0, None), (1, '5pm'), (2, None)]
>>> list(G.nodes.data("time"))
[(0, None), (1, '5pm'), (2, None)]
>>> list(G.nodes(data="time", default="Not Available"))
[(0, 'Not Available'), (1, '5pm'), (2, 'Not Available')]
>>> list(G.nodes.data("time", default="Not Available"))
[(0, 'Not Available'), (1, '5pm'), (2, 'Not Available')]
If some of your nodes have an attribute and the rest are assumed
to have a default attribute value you can create a dictionary
from node/attribute pairs using the `default` keyword argument
to guarantee the value is never None::
>>> G = nx.Graph()
>>> G.add_node(0)
>>> G.add_node(1, weight=2)
>>> G.add_node(2, weight=3)
>>> dict(G.nodes(data="weight", default=1))
{0: 1, 1: 2, 2: 3}
"""
return NodeView(self)
def number_of_nodes(self):
"""Returns the number of nodes in the graph.
Returns
-------
nnodes : int
The number of nodes in the graph.
See Also
--------
order: identical method
__len__: identical method
Examples
--------
>>> G = nx.path_graph(3) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.number_of_nodes()
3
"""
return len(self._node)
def order(self):
"""Returns the number of nodes in the graph.
Returns
-------
nnodes : int
The number of nodes in the graph.
See Also
--------
number_of_nodes: identical method
__len__: identical method
Examples
--------
>>> G = nx.path_graph(3) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.order()
3
"""
return len(self._node)
def has_node(self, n):
"""Returns True if the graph contains the node n.
Identical to `n in G`
Parameters
----------
n : node
Examples
--------
>>> G = nx.path_graph(3) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.has_node(0)
True
It is more readable and simpler to use
>>> 0 in G
True
"""
try:
return n in self._node
except TypeError:
return False
def add_edge(self, u_of_edge, v_of_edge, **attr):
"""Add an edge between u and v.
The nodes u and v will be automatically added if they are
not already in the graph.
Edge attributes can be specified with keywords or by directly
accessing the edge's attribute dictionary. See examples below.
Parameters
----------
u_of_edge, v_of_edge : nodes
Nodes can be, for example, strings or numbers.
Nodes must be hashable (and not None) Python objects.
attr : keyword arguments, optional
Edge data (or labels or objects) can be assigned using
keyword arguments.
See Also
--------
add_edges_from : add a collection of edges
Notes
-----
Adding an edge that already exists updates the edge data.
Many NetworkX algorithms designed for weighted graphs use
an edge attribute (by default `weight`) to hold a numerical value.
Examples
--------
The following all add the edge e=(1, 2) to graph G:
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> e = (1, 2)
>>> G.add_edge(1, 2) # explicit two-node form
>>> G.add_edge(*e) # single edge as tuple of two nodes
>>> G.add_edges_from([(1, 2)]) # add edges from iterable container
Associate data to edges using keywords:
>>> G.add_edge(1, 2, weight=3)
>>> G.add_edge(1, 3, weight=7, capacity=15, length=342.7)
For non-string attribute keys, use subscript notation.
>>> G.add_edge(1, 2)
>>> G[1][2].update({0: 5})
>>> G.edges[1, 2].update({0: 5})
"""
u, v = u_of_edge, v_of_edge
# add nodes
if u not in self._node:
if u is None:
raise ValueError("None cannot be a node")
self._adj[u] = self.adjlist_inner_dict_factory()
self._node[u] = self.node_attr_dict_factory()
if v not in self._node:
if v is None:
raise ValueError("None cannot be a node")
self._adj[v] = self.adjlist_inner_dict_factory()
self._node[v] = self.node_attr_dict_factory()
# add the edge
datadict = self._adj[u].get(v, self.edge_attr_dict_factory())
datadict.update(attr)
self._adj[u][v] = datadict
self._adj[v][u] = datadict
nx._clear_cache(self)
def add_edges_from(self, ebunch_to_add, **attr):
"""Add all the edges in ebunch_to_add.
Parameters
----------
ebunch_to_add : container of edges
Each edge given in the container will be added to the
graph. The edges must be given as 2-tuples (u, v) or
3-tuples (u, v, d) where d is a dictionary containing edge data.
attr : keyword arguments, optional
Edge data (or labels or objects) can be assigned using
keyword arguments.
See Also
--------
add_edge : add a single edge
add_weighted_edges_from : convenient way to add weighted edges
Notes
-----
Adding the same edge twice has no effect but any edge data
will be updated when each duplicate edge is added.
Edge attributes specified in an ebunch take precedence over
attributes specified via keyword arguments.
When adding edges from an iterator over the graph you are changing,
a `RuntimeError` can be raised with message:
`RuntimeError: dictionary changed size during iteration`. This
happens when the graph's underlying dictionary is modified during
iteration. To avoid this error, evaluate the iterator into a separate
object, e.g. by using `list(iterator_of_edges)`, and pass this
object to `G.add_edges_from`.
Examples
--------
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.add_edges_from([(0, 1), (1, 2)]) # using a list of edge tuples
>>> e = zip(range(0, 3), range(1, 4))
>>> G.add_edges_from(e) # Add the path graph 0-1-2-3
Associate data to edges
>>> G.add_edges_from([(1, 2), (2, 3)], weight=3)
>>> G.add_edges_from([(3, 4), (1, 4)], label="WN2898")
Evaluate an iterator over a graph if using it to modify the same graph
>>> G = nx.Graph([(1, 2), (2, 3), (3, 4)])
>>> # Grow graph by one new node, adding edges to all existing nodes.
>>> # wrong way - will raise RuntimeError
>>> # G.add_edges_from(((5, n) for n in G.nodes))
>>> # correct way - note that there will be no self-edge for node 5
>>> G.add_edges_from(list((5, n) for n in G.nodes))
"""
for e in ebunch_to_add:
ne = len(e)
if ne == 3:
u, v, dd = e
elif ne == 2:
u, v = e
dd = {} # doesn't need edge_attr_dict_factory
else:
raise NetworkXError(f"Edge tuple {e} must be a 2-tuple or 3-tuple.")
if u not in self._node:
if u is None:
raise ValueError("None cannot be a node")
self._adj[u] = self.adjlist_inner_dict_factory()
self._node[u] = self.node_attr_dict_factory()
if v not in self._node:
if v is None:
raise ValueError("None cannot be a node")
self._adj[v] = self.adjlist_inner_dict_factory()
self._node[v] = self.node_attr_dict_factory()
datadict = self._adj[u].get(v, self.edge_attr_dict_factory())
datadict.update(attr)
datadict.update(dd)
self._adj[u][v] = datadict
self._adj[v][u] = datadict
nx._clear_cache(self)
def add_weighted_edges_from(self, ebunch_to_add, weight="weight", **attr):
"""Add weighted edges in `ebunch_to_add` with specified weight attr
Parameters
----------
ebunch_to_add : container of edges
Each edge given in the list or container will be added
to the graph. The edges must be given as 3-tuples (u, v, w)
where w is a number.
weight : string, optional (default= 'weight')
The attribute name for the edge weights to be added.
attr : keyword arguments, optional (default= no attributes)
Edge attributes to add/update for all edges.
See Also
--------
add_edge : add a single edge
add_edges_from : add multiple edges
Notes
-----
Adding the same edge twice for Graph/DiGraph simply updates
the edge data. For MultiGraph/MultiDiGraph, duplicate edges
are stored.
When adding edges from an iterator over the graph you are changing,
a `RuntimeError` can be raised with message:
`RuntimeError: dictionary changed size during iteration`. This
happens when the graph's underlying dictionary is modified during
iteration. To avoid this error, evaluate the iterator into a separate
object, e.g. by using `list(iterator_of_edges)`, and pass this
object to `G.add_weighted_edges_from`.
Examples
--------
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.add_weighted_edges_from([(0, 1, 3.0), (1, 2, 7.5)])
Evaluate an iterator over edges before passing it
>>> G = nx.Graph([(1, 2), (2, 3), (3, 4)])
>>> weight = 0.1
>>> # Grow graph by one new node, adding edges to all existing nodes.
>>> # wrong way - will raise RuntimeError
>>> # G.add_weighted_edges_from(((5, n, weight) for n in G.nodes))
>>> # correct way - note that there will be no self-edge for node 5
>>> G.add_weighted_edges_from(list((5, n, weight) for n in G.nodes))
"""
self.add_edges_from(((u, v, {weight: d}) for u, v, d in ebunch_to_add), **attr)
nx._clear_cache(self)
def remove_edge(self, u, v):
"""Remove the edge between u and v.
Parameters
----------
u, v : nodes
Remove the edge between nodes u and v.
Raises
------
NetworkXError
If there is not an edge between u and v.
See Also
--------
remove_edges_from : remove a collection of edges
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, etc
>>> G.remove_edge(0, 1)
>>> e = (1, 2)
>>> G.remove_edge(*e) # unpacks e from an edge tuple
>>> e = (2, 3, {"weight": 7}) # an edge with attribute data
>>> G.remove_edge(*e[:2]) # select first part of edge tuple
"""
try:
del self._adj[u][v]
if u != v: # self-loop needs only one entry removed
del self._adj[v][u]
except KeyError as err:
raise NetworkXError(f"The edge {u}-{v} is not in the graph") from err
nx._clear_cache(self)
def remove_edges_from(self, ebunch):
"""Remove all edges specified in ebunch.
Parameters
----------
ebunch: list or container of edge tuples
Each edge given in the list or container will be removed
from the graph. The edges can be:
- 2-tuples (u, v) edge between u and v.
- 3-tuples (u, v, k) where k is ignored.
See Also
--------
remove_edge : remove a single edge
Notes
-----
Will fail silently if an edge in ebunch is not in the graph.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> ebunch = [(1, 2), (2, 3)]
>>> G.remove_edges_from(ebunch)
"""
adj = self._adj
for e in ebunch:
u, v = e[:2] # ignore edge data if present
if u in adj and v in adj[u]:
del adj[u][v]
if u != v: # self loop needs only one entry removed
del adj[v][u]
nx._clear_cache(self)
def update(self, edges=None, nodes=None):
"""Update the graph using nodes/edges/graphs as input.
Like dict.update, this method takes a graph as input, adding the
graph's nodes and edges to this graph. It can also take two inputs:
edges and nodes. Finally it can take either edges or nodes.
To specify only nodes the keyword `nodes` must be used.
The collections of edges and nodes are treated similarly to
the add_edges_from/add_nodes_from methods. When iterated, they
should yield 2-tuples (u, v) or 3-tuples (u, v, datadict).
Parameters
----------
edges : Graph object, collection of edges, or None
The first parameter can be a graph or some edges. If it has
attributes `nodes` and `edges`, then it is taken to be a
Graph-like object and those attributes are used as collections
of nodes and edges to be added to the graph.
If the first parameter does not have those attributes, it is
treated as a collection of edges and added to the graph.
If the first argument is None, no edges are added.
nodes : collection of nodes, or None
The second parameter is treated as a collection of nodes
to be added to the graph unless it is None.
If `edges is None` and `nodes is None` an exception is raised.
If the first parameter is a Graph, then `nodes` is ignored.
Examples
--------
>>> G = nx.path_graph(5)
>>> G.update(nx.complete_graph(range(4, 10)))
>>> from itertools import combinations
>>> edges = (
... (u, v, {"power": u * v})
... for u, v in combinations(range(10, 20), 2)
... if u * v < 225
... )
>>> nodes = [1000] # for singleton, use a container
>>> G.update(edges, nodes)
Notes
-----
It you want to update the graph using an adjacency structure
it is straightforward to obtain the edges/nodes from adjacency.
The following examples provide common cases, your adjacency may
be slightly different and require tweaks of these examples::
>>> # dict-of-set/list/tuple
>>> adj = {1: {2, 3}, 2: {1, 3}, 3: {1, 2}}
>>> e = [(u, v) for u, nbrs in adj.items() for v in nbrs]
>>> G.update(edges=e, nodes=adj)
>>> DG = nx.DiGraph()
>>> # dict-of-dict-of-attribute
>>> adj = {1: {2: 1.3, 3: 0.7}, 2: {1: 1.4}, 3: {1: 0.7}}
>>> e = [(u, v, {"weight": d}) for u, nbrs in adj.items() for v, d in nbrs.items()]
>>> DG.update(edges=e, nodes=adj)
>>> # dict-of-dict-of-dict
>>> adj = {1: {2: {"weight": 1.3}, 3: {"color": 0.7, "weight": 1.2}}}
>>> e = [(u, v, {"weight": d}) for u, nbrs in adj.items() for v, d in nbrs.items()]
>>> DG.update(edges=e, nodes=adj)
>>> # predecessor adjacency (dict-of-set)
>>> pred = {1: {2, 3}, 2: {3}, 3: {3}}
>>> e = [(v, u) for u, nbrs in pred.items() for v in nbrs]
>>> # MultiGraph dict-of-dict-of-dict-of-attribute
>>> MDG = nx.MultiDiGraph()
>>> adj = {
... 1: {2: {0: {"weight": 1.3}, 1: {"weight": 1.2}}},
... 3: {2: {0: {"weight": 0.7}}},
... }
>>> e = [
... (u, v, ekey, d)
... for u, nbrs in adj.items()
... for v, keydict in nbrs.items()
... for ekey, d in keydict.items()
... ]
>>> MDG.update(edges=e)
See Also
--------
add_edges_from: add multiple edges to a graph
add_nodes_from: add multiple nodes to a graph
"""
if edges is not None:
if nodes is not None:
self.add_nodes_from(nodes)
self.add_edges_from(edges)
else:
# check if edges is a Graph object
try:
graph_nodes = edges.nodes
graph_edges = edges.edges
except AttributeError:
# edge not Graph-like
self.add_edges_from(edges)
else: # edges is Graph-like
self.add_nodes_from(graph_nodes.data())
self.add_edges_from(graph_edges.data())
self.graph.update(edges.graph)
elif nodes is not None:
self.add_nodes_from(nodes)
else:
raise NetworkXError("update needs nodes or edges input")
def has_edge(self, u, v):
"""Returns True if the edge (u, v) is in the graph.
This is the same as `v in G[u]` without KeyError exceptions.
Parameters
----------
u, v : nodes
Nodes can be, for example, strings or numbers.
Nodes must be hashable (and not None) Python objects.
Returns
-------
edge_ind : bool
True if edge is in the graph, False otherwise.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.has_edge(0, 1) # using two nodes
True
>>> e = (0, 1)
>>> G.has_edge(*e) # e is a 2-tuple (u, v)
True
>>> e = (0, 1, {"weight": 7})
>>> G.has_edge(*e[:2]) # e is a 3-tuple (u, v, data_dictionary)
True
The following syntax are equivalent:
>>> G.has_edge(0, 1)
True
>>> 1 in G[0] # though this gives KeyError if 0 not in G
True
"""
try:
return v in self._adj[u]
except KeyError:
return False
def neighbors(self, n):
"""Returns an iterator over all neighbors of node n.
This is identical to `iter(G[n])`
Parameters
----------
n : node
A node in the graph
Returns
-------
neighbors : iterator
An iterator over all neighbors of node n
Raises
------
NetworkXError
If the node n is not in the graph.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> [n for n in G.neighbors(0)]
[1]
Notes
-----
Alternate ways to access the neighbors are ``G.adj[n]`` or ``G[n]``:
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.add_edge("a", "b", weight=7)
>>> G["a"]
AtlasView({'b': {'weight': 7}})
>>> G = nx.path_graph(4)
>>> [n for n in G[0]]
[1]
"""
try:
return iter(self._adj[n])
except KeyError as err:
raise NetworkXError(f"The node {n} is not in the graph.") from err
@cached_property
def edges(self):
"""An EdgeView of the Graph as G.edges or G.edges().
edges(self, nbunch=None, data=False, default=None)
The EdgeView provides set-like operations on the edge-tuples
as well as edge attribute lookup. When called, it also provides
an EdgeDataView object which allows control of access to edge
attributes (but does not provide set-like operations).
Hence, `G.edges[u, v]['color']` provides the value of the color
attribute for edge `(u, v)` while
`for (u, v, c) in G.edges.data('color', default='red'):`
iterates through all the edges yielding the color attribute
with default `'red'` if no color attribute exists.
Parameters
----------
nbunch : single node, container, or all nodes (default= all nodes)
The view will only report edges from these nodes.
data : string or bool, optional (default=False)
The edge attribute returned in 3-tuple (u, v, ddict[data]).
If True, return edge attribute dict in 3-tuple (u, v, ddict).
If False, return 2-tuple (u, v).
default : value, optional (default=None)
Value used for edges that don't have the requested attribute.
Only relevant if data is not True or False.
Returns
-------
edges : EdgeView
A view of edge attributes, usually it iterates over (u, v)
or (u, v, d) tuples of edges, but can also be used for
attribute lookup as `edges[u, v]['foo']`.
Notes
-----
Nodes in nbunch that are not in the graph will be (quietly) ignored.
For directed graphs this returns the out-edges.
Examples
--------
>>> G = nx.path_graph(3) # or MultiGraph, etc
>>> G.add_edge(2, 3, weight=5)
>>> [e for e in G.edges]
[(0, 1), (1, 2), (2, 3)]
>>> G.edges.data() # default data is {} (empty dict)
EdgeDataView([(0, 1, {}), (1, 2, {}), (2, 3, {'weight': 5})])
>>> G.edges.data("weight", default=1)
EdgeDataView([(0, 1, 1), (1, 2, 1), (2, 3, 5)])
>>> G.edges([0, 3]) # only edges from these nodes
EdgeDataView([(0, 1), (3, 2)])
>>> G.edges(0) # only edges from node 0
EdgeDataView([(0, 1)])
"""
return EdgeView(self)
def get_edge_data(self, u, v, default=None):
"""Returns the attribute dictionary associated with edge (u, v).
This is identical to `G[u][v]` except the default is returned
instead of an exception if the edge doesn't exist.
Parameters
----------
u, v : nodes
default: any Python object (default=None)
Value to return if the edge (u, v) is not found.
Returns
-------
edge_dict : dictionary
The edge attribute dictionary.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G[0][1]
{}
Warning: Assigning to `G[u][v]` is not permitted.
But it is safe to assign attributes `G[u][v]['foo']`
>>> G[0][1]["weight"] = 7
>>> G[0][1]["weight"]
7
>>> G[1][0]["weight"]
7
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.get_edge_data(0, 1) # default edge data is {}
{}
>>> e = (0, 1)
>>> G.get_edge_data(*e) # tuple form
{}
>>> G.get_edge_data("a", "b", default=0) # edge not in graph, return 0
0
"""
try:
return self._adj[u][v]
except KeyError:
return default
def adjacency(self):
"""Returns an iterator over (node, adjacency dict) tuples for all nodes.
For directed graphs, only outgoing neighbors/adjacencies are included.
Returns
-------
adj_iter : iterator
An iterator over (node, adjacency dictionary) for all nodes in
the graph.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> [(n, nbrdict) for n, nbrdict in G.adjacency()]
[(0, {1: {}}), (1, {0: {}, 2: {}}), (2, {1: {}, 3: {}}), (3, {2: {}})]
"""
return iter(self._adj.items())
@cached_property
def degree(self):
"""A DegreeView for the Graph as G.degree or G.degree().
The node degree is the number of edges adjacent to the node.
The weighted node degree is the sum of the edge weights for
edges incident to that node.
This object provides an iterator for (node, degree) as well as
lookup for the degree for a single node.
Parameters
----------
nbunch : single node, container, or all nodes (default= all nodes)
The view will only report edges incident to these nodes.
weight : string or None, optional (default=None)
The name of an edge attribute that holds the numerical value used
as a weight. If None, then each edge has weight 1.
The degree is the sum of the edge weights adjacent to the node.
Returns
-------
DegreeView or int
If multiple nodes are requested (the default), returns a `DegreeView`
mapping nodes to their degree.
If a single node is requested, returns the degree of the node as an integer.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.degree[0] # node 0 has degree 1
1
>>> list(G.degree([0, 1, 2]))
[(0, 1), (1, 2), (2, 2)]
"""
return DegreeView(self)
def clear(self):
"""Remove all nodes and edges from the graph.
This also removes the name, and all graph, node, and edge attributes.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.clear()
>>> list(G.nodes)
[]
>>> list(G.edges)
[]
"""
self._adj.clear()
self._node.clear()
self.graph.clear()
nx._clear_cache(self)
def clear_edges(self):
"""Remove all edges from the graph without altering nodes.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.clear_edges()
>>> list(G.nodes)
[0, 1, 2, 3]
>>> list(G.edges)
[]
"""
for nbr_dict in self._adj.values():
nbr_dict.clear()
nx._clear_cache(self)
def is_multigraph(self):
"""Returns True if graph is a multigraph, False otherwise."""
return False
def is_directed(self):
"""Returns True if graph is directed, False otherwise."""
return False
def copy(self, as_view=False):
"""Returns a copy of the graph.
The copy method by default returns an independent shallow copy
of the graph and attributes. That is, if an attribute is a
container, that container is shared by the original an the copy.
Use Python's `copy.deepcopy` for new containers.
If `as_view` is True then a view is returned instead of a copy.
Notes
-----
All copies reproduce the graph structure, but data attributes
may be handled in different ways. There are four types of copies
of a graph that people might want.
Deepcopy -- A "deepcopy" copies the graph structure as well as
all data attributes and any objects they might contain.
The entire graph object is new so that changes in the copy
do not affect the original object. (see Python's copy.deepcopy)
Data Reference (Shallow) -- For a shallow copy the graph structure
is copied but the edge, node and graph attribute dicts are
references to those in the original graph. This saves
time and memory but could cause confusion if you change an attribute
in one graph and it changes the attribute in the other.
NetworkX does not provide this level of shallow copy.
Independent Shallow -- This copy creates new independent attribute
dicts and then does a shallow copy of the attributes. That is, any
attributes that are containers are shared between the new graph
and the original. This is exactly what `dict.copy()` provides.
You can obtain this style copy using:
>>> G = nx.path_graph(5)
>>> H = G.copy()
>>> H = G.copy(as_view=False)
>>> H = nx.Graph(G)
>>> H = G.__class__(G)
Fresh Data -- For fresh data, the graph structure is copied while
new empty data attribute dicts are created. The resulting graph
is independent of the original and it has no edge, node or graph
attributes. Fresh copies are not enabled. Instead use:
>>> H = G.__class__()
>>> H.add_nodes_from(G)
>>> H.add_edges_from(G.edges)
View -- Inspired by dict-views, graph-views act like read-only
versions of the original graph, providing a copy of the original
structure without requiring any memory for copying the information.
See the Python copy module for more information on shallow
and deep copies, https://docs.python.org/3/library/copy.html.
Parameters
----------
as_view : bool, optional (default=False)
If True, the returned graph-view provides a read-only view
of the original graph without actually copying any data.
Returns
-------
G : Graph
A copy of the graph.
See Also
--------
to_directed: return a directed copy of the graph.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> H = G.copy()
"""
if as_view is True:
return nx.graphviews.generic_graph_view(self)
G = self.__class__()
G.graph.update(self.graph)
G.add_nodes_from((n, d.copy()) for n, d in self._node.items())
G.add_edges_from(
(u, v, datadict.copy())
for u, nbrs in self._adj.items()
for v, datadict in nbrs.items()
)
return G
def to_directed(self, as_view=False):
"""Returns a directed representation of the graph.
Returns
-------
G : DiGraph
A directed graph with the same name, same nodes, and with
each edge (u, v, data) replaced by two directed edges
(u, v, data) and (v, u, data).
Notes
-----
This returns a "deepcopy" of the edge, node, and
graph attributes which attempts to completely copy
all of the data and references.
This is in contrast to the similar D=DiGraph(G) which returns a
shallow copy of the data.
See the Python copy module for more information on shallow
and deep copies, https://docs.python.org/3/library/copy.html.
Warning: If you have subclassed Graph to use dict-like objects
in the data structure, those changes do not transfer to the
DiGraph created by this method.
Examples
--------
>>> G = nx.Graph() # or MultiGraph, etc
>>> G.add_edge(0, 1)
>>> H = G.to_directed()
>>> list(H.edges)
[(0, 1), (1, 0)]
If already directed, return a (deep) copy
>>> G = nx.DiGraph() # or MultiDiGraph, etc
>>> G.add_edge(0, 1)
>>> H = G.to_directed()
>>> list(H.edges)
[(0, 1)]
"""
graph_class = self.to_directed_class()
if as_view is True:
return nx.graphviews.generic_graph_view(self, graph_class)
# deepcopy when not a view
G = graph_class()
G.graph.update(deepcopy(self.graph))
G.add_nodes_from((n, deepcopy(d)) for n, d in self._node.items())
G.add_edges_from(
(u, v, deepcopy(data))
for u, nbrs in self._adj.items()
for v, data in nbrs.items()
)
return G
def to_undirected(self, as_view=False):
"""Returns an undirected copy of the graph.
Parameters
----------
as_view : bool (optional, default=False)
If True return a view of the original undirected graph.
Returns
-------
G : Graph/MultiGraph
A deepcopy of the graph.
See Also
--------
Graph, copy, add_edge, add_edges_from
Notes
-----
This returns a "deepcopy" of the edge, node, and
graph attributes which attempts to completely copy
all of the data and references.
This is in contrast to the similar `G = nx.DiGraph(D)` which returns a
shallow copy of the data.
See the Python copy module for more information on shallow
and deep copies, https://docs.python.org/3/library/copy.html.
Warning: If you have subclassed DiGraph to use dict-like objects
in the data structure, those changes do not transfer to the
Graph created by this method.
Examples
--------
>>> G = nx.path_graph(2) # or MultiGraph, etc
>>> H = G.to_directed()
>>> list(H.edges)
[(0, 1), (1, 0)]
>>> G2 = H.to_undirected()
>>> list(G2.edges)
[(0, 1)]
"""
graph_class = self.to_undirected_class()
if as_view is True:
return nx.graphviews.generic_graph_view(self, graph_class)
# deepcopy when not a view
G = graph_class()
G.graph.update(deepcopy(self.graph))
G.add_nodes_from((n, deepcopy(d)) for n, d in self._node.items())
G.add_edges_from(
(u, v, deepcopy(d))
for u, nbrs in self._adj.items()
for v, d in nbrs.items()
)
return G
def subgraph(self, nodes):
"""Returns a SubGraph view of the subgraph induced on `nodes`.
The induced subgraph of the graph contains the nodes in `nodes`
and the edges between those nodes.
Parameters
----------
nodes : list, iterable
A container of nodes which will be iterated through once.
Returns
-------
G : SubGraph View
A subgraph view of the graph. The graph structure cannot be
changed but node/edge attributes can and are shared with the
original graph.
Notes
-----
The graph, edge and node attributes are shared with the original graph.
Changes to the graph structure is ruled out by the view, but changes
to attributes are reflected in the original graph.
To create a subgraph with its own copy of the edge/node attributes use:
G.subgraph(nodes).copy()
For an inplace reduction of a graph to a subgraph you can remove nodes:
G.remove_nodes_from([n for n in G if n not in set(nodes)])
Subgraph views are sometimes NOT what you want. In most cases where
you want to do more than simply look at the induced edges, it makes
more sense to just create the subgraph as its own graph with code like:
::
# Create a subgraph SG based on a (possibly multigraph) G
SG = G.__class__()
SG.add_nodes_from((n, G.nodes[n]) for n in largest_wcc)
if SG.is_multigraph():
SG.add_edges_from(
(n, nbr, key, d)
for n, nbrs in G.adj.items()
if n in largest_wcc
for nbr, keydict in nbrs.items()
if nbr in largest_wcc
for key, d in keydict.items()
)
else:
SG.add_edges_from(
(n, nbr, d)
for n, nbrs in G.adj.items()
if n in largest_wcc
for nbr, d in nbrs.items()
if nbr in largest_wcc
)
SG.graph.update(G.graph)
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> H = G.subgraph([0, 1, 2])
>>> list(H.edges)
[(0, 1), (1, 2)]
"""
induced_nodes = nx.filters.show_nodes(self.nbunch_iter(nodes))
# if already a subgraph, don't make a chain
subgraph = nx.subgraph_view
if hasattr(self, "_NODE_OK"):
return subgraph(
self._graph, filter_node=induced_nodes, filter_edge=self._EDGE_OK
)
return subgraph(self, filter_node=induced_nodes)
def edge_subgraph(self, edges):
"""Returns the subgraph induced by the specified edges.
The induced subgraph contains each edge in `edges` and each
node incident to any one of those edges.
Parameters
----------
edges : iterable
An iterable of edges in this graph.
Returns
-------
G : Graph
An edge-induced subgraph of this graph with the same edge
attributes.
Notes
-----
The graph, edge, and node attributes in the returned subgraph
view are references to the corresponding attributes in the original
graph. The view is read-only.
To create a full graph version of the subgraph with its own copy
of the edge or node attributes, use::
G.edge_subgraph(edges).copy()
Examples
--------
>>> G = nx.path_graph(5)
>>> H = G.edge_subgraph([(0, 1), (3, 4)])
>>> list(H.nodes)
[0, 1, 3, 4]
>>> list(H.edges)
[(0, 1), (3, 4)]
"""
return nx.edge_subgraph(self, edges)
def size(self, weight=None):
"""Returns the number of edges or total of all edge weights.
Parameters
----------
weight : string or None, optional (default=None)
The edge attribute that holds the numerical value used
as a weight. If None, then each edge has weight 1.
Returns
-------
size : numeric
The number of edges or
(if weight keyword is provided) the total weight sum.
If weight is None, returns an int. Otherwise a float
(or more general numeric if the weights are more general).
See Also
--------
number_of_edges
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.size()
3
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.add_edge("a", "b", weight=2)
>>> G.add_edge("b", "c", weight=4)
>>> G.size()
2
>>> G.size(weight="weight")
6.0
"""
s = sum(d for v, d in self.degree(weight=weight))
# If `weight` is None, the sum of the degrees is guaranteed to be
# even, so we can perform integer division and hence return an
# integer. Otherwise, the sum of the weighted degrees is not
# guaranteed to be an integer, so we perform "real" division.
return s // 2 if weight is None else s / 2
def number_of_edges(self, u=None, v=None):
"""Returns the number of edges between two nodes.
Parameters
----------
u, v : nodes, optional (default=all edges)
If u and v are specified, return the number of edges between
u and v. Otherwise return the total number of all edges.
Returns
-------
nedges : int
The number of edges in the graph. If nodes `u` and `v` are
specified return the number of edges between those nodes. If
the graph is directed, this only returns the number of edges
from `u` to `v`.
See Also
--------
size
Examples
--------
For undirected graphs, this method counts the total number of
edges in the graph:
>>> G = nx.path_graph(4)
>>> G.number_of_edges()
3
If you specify two nodes, this counts the total number of edges
joining the two nodes:
>>> G.number_of_edges(0, 1)
1
For directed graphs, this method can count the total number of
directed edges from `u` to `v`:
>>> G = nx.DiGraph()
>>> G.add_edge(0, 1)
>>> G.add_edge(1, 0)
>>> G.number_of_edges(0, 1)
1
"""
if u is None:
return int(self.size())
if v in self._adj[u]:
return 1
return 0
def nbunch_iter(self, nbunch=None):
"""Returns an iterator over nodes contained in nbunch that are
also in the graph.
The nodes in nbunch are checked for membership in the graph
and if not are silently ignored.
Parameters
----------
nbunch : single node, container, or all nodes (default= all nodes)
The view will only report edges incident to these nodes.
Returns
-------
niter : iterator
An iterator over nodes in nbunch that are also in the graph.
If nbunch is None, iterate over all nodes in the graph.
Raises
------
NetworkXError
If nbunch is not a node or sequence of nodes.
If a node in nbunch is not hashable.
See Also
--------
Graph.__iter__
Notes
-----
When nbunch is an iterator, the returned iterator yields values
directly from nbunch, becoming exhausted when nbunch is exhausted.
To test whether nbunch is a single node, one can use
"if nbunch in self:", even after processing with this routine.
If nbunch is not a node or a (possibly empty) sequence/iterator
or None, a :exc:`NetworkXError` is raised. Also, if any object in
nbunch is not hashable, a :exc:`NetworkXError` is raised.
"""
if nbunch is None: # include all nodes via iterator
bunch = iter(self._adj)
elif nbunch in self: # if nbunch is a single node
bunch = iter([nbunch])
else: # if nbunch is a sequence of nodes
def bunch_iter(nlist, adj):
try:
for n in nlist:
if n in adj:
yield n
except TypeError as err:
exc, message = err, err.args[0]
# capture error for non-sequence/iterator nbunch.
if "iter" in message:
exc = NetworkXError(
"nbunch is not a node or a sequence of nodes."
)
# capture error for unhashable node.
if "hashable" in message:
exc = NetworkXError(
f"Node {n} in sequence nbunch is not a valid node."
)
raise exc
bunch = bunch_iter(nbunch, self._adj)
return bunch
| (incoming_graph_data=None, **attr) |
30,113 | networkx.classes.graph | __init__ | Initialize a graph with edges, name, or graph attributes.
Parameters
----------
incoming_graph_data : input graph (optional, default: None)
Data to initialize graph. If None (default) an empty
graph is created. The data can be an edge list, or any
NetworkX graph object. If the corresponding optional Python
packages are installed the data can also be a 2D NumPy array, a
SciPy sparse array, or a PyGraphviz graph.
attr : keyword arguments, optional (default= no attributes)
Attributes to add to graph as key=value pairs.
See Also
--------
convert
Examples
--------
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G = nx.Graph(name="my graph")
>>> e = [(1, 2), (2, 3), (3, 4)] # list of edges
>>> G = nx.Graph(e)
Arbitrary graph attribute pairs (key=value) may be assigned
>>> G = nx.Graph(e, day="Friday")
>>> G.graph
{'day': 'Friday'}
| def __init__(self, incoming_graph_data=None, **attr):
"""Initialize a graph with edges, name, or graph attributes.
Parameters
----------
incoming_graph_data : input graph (optional, default: None)
Data to initialize graph. If None (default) an empty
graph is created. The data can be an edge list, or any
NetworkX graph object. If the corresponding optional Python
packages are installed the data can also be a 2D NumPy array, a
SciPy sparse array, or a PyGraphviz graph.
attr : keyword arguments, optional (default= no attributes)
Attributes to add to graph as key=value pairs.
See Also
--------
convert
Examples
--------
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G = nx.Graph(name="my graph")
>>> e = [(1, 2), (2, 3), (3, 4)] # list of edges
>>> G = nx.Graph(e)
Arbitrary graph attribute pairs (key=value) may be assigned
>>> G = nx.Graph(e, day="Friday")
>>> G.graph
{'day': 'Friday'}
"""
self.graph = self.graph_attr_dict_factory() # dictionary for graph attributes
self._node = self.node_dict_factory() # empty node attribute dict
self._adj = self.adjlist_outer_dict_factory() # empty adjacency dict
self.__networkx_cache__ = {}
# attempt to load graph with data
if incoming_graph_data is not None:
convert.to_networkx_graph(incoming_graph_data, create_using=self)
# load graph attributes (must be after convert)
self.graph.update(attr)
| (self, incoming_graph_data=None, **attr) |
30,117 | networkx.classes.graph | add_edge | Add an edge between u and v.
The nodes u and v will be automatically added if they are
not already in the graph.
Edge attributes can be specified with keywords or by directly
accessing the edge's attribute dictionary. See examples below.
Parameters
----------
u_of_edge, v_of_edge : nodes
Nodes can be, for example, strings or numbers.
Nodes must be hashable (and not None) Python objects.
attr : keyword arguments, optional
Edge data (or labels or objects) can be assigned using
keyword arguments.
See Also
--------
add_edges_from : add a collection of edges
Notes
-----
Adding an edge that already exists updates the edge data.
Many NetworkX algorithms designed for weighted graphs use
an edge attribute (by default `weight`) to hold a numerical value.
Examples
--------
The following all add the edge e=(1, 2) to graph G:
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> e = (1, 2)
>>> G.add_edge(1, 2) # explicit two-node form
>>> G.add_edge(*e) # single edge as tuple of two nodes
>>> G.add_edges_from([(1, 2)]) # add edges from iterable container
Associate data to edges using keywords:
>>> G.add_edge(1, 2, weight=3)
>>> G.add_edge(1, 3, weight=7, capacity=15, length=342.7)
For non-string attribute keys, use subscript notation.
>>> G.add_edge(1, 2)
>>> G[1][2].update({0: 5})
>>> G.edges[1, 2].update({0: 5})
| def add_edge(self, u_of_edge, v_of_edge, **attr):
"""Add an edge between u and v.
The nodes u and v will be automatically added if they are
not already in the graph.
Edge attributes can be specified with keywords or by directly
accessing the edge's attribute dictionary. See examples below.
Parameters
----------
u_of_edge, v_of_edge : nodes
Nodes can be, for example, strings or numbers.
Nodes must be hashable (and not None) Python objects.
attr : keyword arguments, optional
Edge data (or labels or objects) can be assigned using
keyword arguments.
See Also
--------
add_edges_from : add a collection of edges
Notes
-----
Adding an edge that already exists updates the edge data.
Many NetworkX algorithms designed for weighted graphs use
an edge attribute (by default `weight`) to hold a numerical value.
Examples
--------
The following all add the edge e=(1, 2) to graph G:
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> e = (1, 2)
>>> G.add_edge(1, 2) # explicit two-node form
>>> G.add_edge(*e) # single edge as tuple of two nodes
>>> G.add_edges_from([(1, 2)]) # add edges from iterable container
Associate data to edges using keywords:
>>> G.add_edge(1, 2, weight=3)
>>> G.add_edge(1, 3, weight=7, capacity=15, length=342.7)
For non-string attribute keys, use subscript notation.
>>> G.add_edge(1, 2)
>>> G[1][2].update({0: 5})
>>> G.edges[1, 2].update({0: 5})
"""
u, v = u_of_edge, v_of_edge
# add nodes
if u not in self._node:
if u is None:
raise ValueError("None cannot be a node")
self._adj[u] = self.adjlist_inner_dict_factory()
self._node[u] = self.node_attr_dict_factory()
if v not in self._node:
if v is None:
raise ValueError("None cannot be a node")
self._adj[v] = self.adjlist_inner_dict_factory()
self._node[v] = self.node_attr_dict_factory()
# add the edge
datadict = self._adj[u].get(v, self.edge_attr_dict_factory())
datadict.update(attr)
self._adj[u][v] = datadict
self._adj[v][u] = datadict
nx._clear_cache(self)
| (self, u_of_edge, v_of_edge, **attr) |
30,118 | networkx.classes.graph | add_edges_from | Add all the edges in ebunch_to_add.
Parameters
----------
ebunch_to_add : container of edges
Each edge given in the container will be added to the
graph. The edges must be given as 2-tuples (u, v) or
3-tuples (u, v, d) where d is a dictionary containing edge data.
attr : keyword arguments, optional
Edge data (or labels or objects) can be assigned using
keyword arguments.
See Also
--------
add_edge : add a single edge
add_weighted_edges_from : convenient way to add weighted edges
Notes
-----
Adding the same edge twice has no effect but any edge data
will be updated when each duplicate edge is added.
Edge attributes specified in an ebunch take precedence over
attributes specified via keyword arguments.
When adding edges from an iterator over the graph you are changing,
a `RuntimeError` can be raised with message:
`RuntimeError: dictionary changed size during iteration`. This
happens when the graph's underlying dictionary is modified during
iteration. To avoid this error, evaluate the iterator into a separate
object, e.g. by using `list(iterator_of_edges)`, and pass this
object to `G.add_edges_from`.
Examples
--------
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.add_edges_from([(0, 1), (1, 2)]) # using a list of edge tuples
>>> e = zip(range(0, 3), range(1, 4))
>>> G.add_edges_from(e) # Add the path graph 0-1-2-3
Associate data to edges
>>> G.add_edges_from([(1, 2), (2, 3)], weight=3)
>>> G.add_edges_from([(3, 4), (1, 4)], label="WN2898")
Evaluate an iterator over a graph if using it to modify the same graph
>>> G = nx.Graph([(1, 2), (2, 3), (3, 4)])
>>> # Grow graph by one new node, adding edges to all existing nodes.
>>> # wrong way - will raise RuntimeError
>>> # G.add_edges_from(((5, n) for n in G.nodes))
>>> # correct way - note that there will be no self-edge for node 5
>>> G.add_edges_from(list((5, n) for n in G.nodes))
| def add_edges_from(self, ebunch_to_add, **attr):
"""Add all the edges in ebunch_to_add.
Parameters
----------
ebunch_to_add : container of edges
Each edge given in the container will be added to the
graph. The edges must be given as 2-tuples (u, v) or
3-tuples (u, v, d) where d is a dictionary containing edge data.
attr : keyword arguments, optional
Edge data (or labels or objects) can be assigned using
keyword arguments.
See Also
--------
add_edge : add a single edge
add_weighted_edges_from : convenient way to add weighted edges
Notes
-----
Adding the same edge twice has no effect but any edge data
will be updated when each duplicate edge is added.
Edge attributes specified in an ebunch take precedence over
attributes specified via keyword arguments.
When adding edges from an iterator over the graph you are changing,
a `RuntimeError` can be raised with message:
`RuntimeError: dictionary changed size during iteration`. This
happens when the graph's underlying dictionary is modified during
iteration. To avoid this error, evaluate the iterator into a separate
object, e.g. by using `list(iterator_of_edges)`, and pass this
object to `G.add_edges_from`.
Examples
--------
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.add_edges_from([(0, 1), (1, 2)]) # using a list of edge tuples
>>> e = zip(range(0, 3), range(1, 4))
>>> G.add_edges_from(e) # Add the path graph 0-1-2-3
Associate data to edges
>>> G.add_edges_from([(1, 2), (2, 3)], weight=3)
>>> G.add_edges_from([(3, 4), (1, 4)], label="WN2898")
Evaluate an iterator over a graph if using it to modify the same graph
>>> G = nx.Graph([(1, 2), (2, 3), (3, 4)])
>>> # Grow graph by one new node, adding edges to all existing nodes.
>>> # wrong way - will raise RuntimeError
>>> # G.add_edges_from(((5, n) for n in G.nodes))
>>> # correct way - note that there will be no self-edge for node 5
>>> G.add_edges_from(list((5, n) for n in G.nodes))
"""
for e in ebunch_to_add:
ne = len(e)
if ne == 3:
u, v, dd = e
elif ne == 2:
u, v = e
dd = {} # doesn't need edge_attr_dict_factory
else:
raise NetworkXError(f"Edge tuple {e} must be a 2-tuple or 3-tuple.")
if u not in self._node:
if u is None:
raise ValueError("None cannot be a node")
self._adj[u] = self.adjlist_inner_dict_factory()
self._node[u] = self.node_attr_dict_factory()
if v not in self._node:
if v is None:
raise ValueError("None cannot be a node")
self._adj[v] = self.adjlist_inner_dict_factory()
self._node[v] = self.node_attr_dict_factory()
datadict = self._adj[u].get(v, self.edge_attr_dict_factory())
datadict.update(attr)
datadict.update(dd)
self._adj[u][v] = datadict
self._adj[v][u] = datadict
nx._clear_cache(self)
| (self, ebunch_to_add, **attr) |
30,119 | networkx.classes.graph | add_node | Add a single node `node_for_adding` and update node attributes.
Parameters
----------
node_for_adding : node
A node can be any hashable Python object except None.
attr : keyword arguments, optional
Set or change node attributes using key=value.
See Also
--------
add_nodes_from
Examples
--------
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.add_node(1)
>>> G.add_node("Hello")
>>> K3 = nx.Graph([(0, 1), (1, 2), (2, 0)])
>>> G.add_node(K3)
>>> G.number_of_nodes()
3
Use keywords set/change node attributes:
>>> G.add_node(1, size=10)
>>> G.add_node(3, weight=0.4, UTM=("13S", 382871, 3972649))
Notes
-----
A hashable object is one that can be used as a key in a Python
dictionary. This includes strings, numbers, tuples of strings
and numbers, etc.
On many platforms hashable items also include mutables such as
NetworkX Graphs, though one should be careful that the hash
doesn't change on mutables.
| def add_node(self, node_for_adding, **attr):
"""Add a single node `node_for_adding` and update node attributes.
Parameters
----------
node_for_adding : node
A node can be any hashable Python object except None.
attr : keyword arguments, optional
Set or change node attributes using key=value.
See Also
--------
add_nodes_from
Examples
--------
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.add_node(1)
>>> G.add_node("Hello")
>>> K3 = nx.Graph([(0, 1), (1, 2), (2, 0)])
>>> G.add_node(K3)
>>> G.number_of_nodes()
3
Use keywords set/change node attributes:
>>> G.add_node(1, size=10)
>>> G.add_node(3, weight=0.4, UTM=("13S", 382871, 3972649))
Notes
-----
A hashable object is one that can be used as a key in a Python
dictionary. This includes strings, numbers, tuples of strings
and numbers, etc.
On many platforms hashable items also include mutables such as
NetworkX Graphs, though one should be careful that the hash
doesn't change on mutables.
"""
if node_for_adding not in self._node:
if node_for_adding is None:
raise ValueError("None cannot be a node")
self._adj[node_for_adding] = self.adjlist_inner_dict_factory()
attr_dict = self._node[node_for_adding] = self.node_attr_dict_factory()
attr_dict.update(attr)
else: # update attr even if node already exists
self._node[node_for_adding].update(attr)
nx._clear_cache(self)
| (self, node_for_adding, **attr) |
30,120 | networkx.classes.graph | add_nodes_from | Add multiple nodes.
Parameters
----------
nodes_for_adding : iterable container
A container of nodes (list, dict, set, etc.).
OR
A container of (node, attribute dict) tuples.
Node attributes are updated using the attribute dict.
attr : keyword arguments, optional (default= no attributes)
Update attributes for all nodes in nodes.
Node attributes specified in nodes as a tuple take
precedence over attributes specified via keyword arguments.
See Also
--------
add_node
Notes
-----
When adding nodes from an iterator over the graph you are changing,
a `RuntimeError` can be raised with message:
`RuntimeError: dictionary changed size during iteration`. This
happens when the graph's underlying dictionary is modified during
iteration. To avoid this error, evaluate the iterator into a separate
object, e.g. by using `list(iterator_of_nodes)`, and pass this
object to `G.add_nodes_from`.
Examples
--------
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.add_nodes_from("Hello")
>>> K3 = nx.Graph([(0, 1), (1, 2), (2, 0)])
>>> G.add_nodes_from(K3)
>>> sorted(G.nodes(), key=str)
[0, 1, 2, 'H', 'e', 'l', 'o']
Use keywords to update specific node attributes for every node.
>>> G.add_nodes_from([1, 2], size=10)
>>> G.add_nodes_from([3, 4], weight=0.4)
Use (node, attrdict) tuples to update attributes for specific nodes.
>>> G.add_nodes_from([(1, dict(size=11)), (2, {"color": "blue"})])
>>> G.nodes[1]["size"]
11
>>> H = nx.Graph()
>>> H.add_nodes_from(G.nodes(data=True))
>>> H.nodes[1]["size"]
11
Evaluate an iterator over a graph if using it to modify the same graph
>>> G = nx.Graph([(0, 1), (1, 2), (3, 4)])
>>> # wrong way - will raise RuntimeError
>>> # G.add_nodes_from(n + 1 for n in G.nodes)
>>> # correct way
>>> G.add_nodes_from(list(n + 1 for n in G.nodes))
| def add_nodes_from(self, nodes_for_adding, **attr):
"""Add multiple nodes.
Parameters
----------
nodes_for_adding : iterable container
A container of nodes (list, dict, set, etc.).
OR
A container of (node, attribute dict) tuples.
Node attributes are updated using the attribute dict.
attr : keyword arguments, optional (default= no attributes)
Update attributes for all nodes in nodes.
Node attributes specified in nodes as a tuple take
precedence over attributes specified via keyword arguments.
See Also
--------
add_node
Notes
-----
When adding nodes from an iterator over the graph you are changing,
a `RuntimeError` can be raised with message:
`RuntimeError: dictionary changed size during iteration`. This
happens when the graph's underlying dictionary is modified during
iteration. To avoid this error, evaluate the iterator into a separate
object, e.g. by using `list(iterator_of_nodes)`, and pass this
object to `G.add_nodes_from`.
Examples
--------
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.add_nodes_from("Hello")
>>> K3 = nx.Graph([(0, 1), (1, 2), (2, 0)])
>>> G.add_nodes_from(K3)
>>> sorted(G.nodes(), key=str)
[0, 1, 2, 'H', 'e', 'l', 'o']
Use keywords to update specific node attributes for every node.
>>> G.add_nodes_from([1, 2], size=10)
>>> G.add_nodes_from([3, 4], weight=0.4)
Use (node, attrdict) tuples to update attributes for specific nodes.
>>> G.add_nodes_from([(1, dict(size=11)), (2, {"color": "blue"})])
>>> G.nodes[1]["size"]
11
>>> H = nx.Graph()
>>> H.add_nodes_from(G.nodes(data=True))
>>> H.nodes[1]["size"]
11
Evaluate an iterator over a graph if using it to modify the same graph
>>> G = nx.Graph([(0, 1), (1, 2), (3, 4)])
>>> # wrong way - will raise RuntimeError
>>> # G.add_nodes_from(n + 1 for n in G.nodes)
>>> # correct way
>>> G.add_nodes_from(list(n + 1 for n in G.nodes))
"""
for n in nodes_for_adding:
try:
newnode = n not in self._node
newdict = attr
except TypeError:
n, ndict = n
newnode = n not in self._node
newdict = attr.copy()
newdict.update(ndict)
if newnode:
if n is None:
raise ValueError("None cannot be a node")
self._adj[n] = self.adjlist_inner_dict_factory()
self._node[n] = self.node_attr_dict_factory()
self._node[n].update(newdict)
nx._clear_cache(self)
| (self, nodes_for_adding, **attr) |
30,123 | networkx.classes.graph | clear | Remove all nodes and edges from the graph.
This also removes the name, and all graph, node, and edge attributes.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.clear()
>>> list(G.nodes)
[]
>>> list(G.edges)
[]
| def clear(self):
"""Remove all nodes and edges from the graph.
This also removes the name, and all graph, node, and edge attributes.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.clear()
>>> list(G.nodes)
[]
>>> list(G.edges)
[]
"""
self._adj.clear()
self._node.clear()
self.graph.clear()
nx._clear_cache(self)
| (self) |
30,124 | networkx.classes.graph | clear_edges | Remove all edges from the graph without altering nodes.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.clear_edges()
>>> list(G.nodes)
[0, 1, 2, 3]
>>> list(G.edges)
[]
| def clear_edges(self):
"""Remove all edges from the graph without altering nodes.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.clear_edges()
>>> list(G.nodes)
[0, 1, 2, 3]
>>> list(G.edges)
[]
"""
for nbr_dict in self._adj.values():
nbr_dict.clear()
nx._clear_cache(self)
| (self) |
30,130 | networkx.classes.graph | is_directed | Returns True if graph is directed, False otherwise. | def is_directed(self):
"""Returns True if graph is directed, False otherwise."""
return False
| (self) |
30,133 | networkx.classes.graph | neighbors | Returns an iterator over all neighbors of node n.
This is identical to `iter(G[n])`
Parameters
----------
n : node
A node in the graph
Returns
-------
neighbors : iterator
An iterator over all neighbors of node n
Raises
------
NetworkXError
If the node n is not in the graph.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> [n for n in G.neighbors(0)]
[1]
Notes
-----
Alternate ways to access the neighbors are ``G.adj[n]`` or ``G[n]``:
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.add_edge("a", "b", weight=7)
>>> G["a"]
AtlasView({'b': {'weight': 7}})
>>> G = nx.path_graph(4)
>>> [n for n in G[0]]
[1]
| def neighbors(self, n):
"""Returns an iterator over all neighbors of node n.
This is identical to `iter(G[n])`
Parameters
----------
n : node
A node in the graph
Returns
-------
neighbors : iterator
An iterator over all neighbors of node n
Raises
------
NetworkXError
If the node n is not in the graph.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> [n for n in G.neighbors(0)]
[1]
Notes
-----
Alternate ways to access the neighbors are ``G.adj[n]`` or ``G[n]``:
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.add_edge("a", "b", weight=7)
>>> G["a"]
AtlasView({'b': {'weight': 7}})
>>> G = nx.path_graph(4)
>>> [n for n in G[0]]
[1]
"""
try:
return iter(self._adj[n])
except KeyError as err:
raise NetworkXError(f"The node {n} is not in the graph.") from err
| (self, n) |
30,137 | networkx.classes.graph | remove_edge | Remove the edge between u and v.
Parameters
----------
u, v : nodes
Remove the edge between nodes u and v.
Raises
------
NetworkXError
If there is not an edge between u and v.
See Also
--------
remove_edges_from : remove a collection of edges
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, etc
>>> G.remove_edge(0, 1)
>>> e = (1, 2)
>>> G.remove_edge(*e) # unpacks e from an edge tuple
>>> e = (2, 3, {"weight": 7}) # an edge with attribute data
>>> G.remove_edge(*e[:2]) # select first part of edge tuple
| def remove_edge(self, u, v):
"""Remove the edge between u and v.
Parameters
----------
u, v : nodes
Remove the edge between nodes u and v.
Raises
------
NetworkXError
If there is not an edge between u and v.
See Also
--------
remove_edges_from : remove a collection of edges
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, etc
>>> G.remove_edge(0, 1)
>>> e = (1, 2)
>>> G.remove_edge(*e) # unpacks e from an edge tuple
>>> e = (2, 3, {"weight": 7}) # an edge with attribute data
>>> G.remove_edge(*e[:2]) # select first part of edge tuple
"""
try:
del self._adj[u][v]
if u != v: # self-loop needs only one entry removed
del self._adj[v][u]
except KeyError as err:
raise NetworkXError(f"The edge {u}-{v} is not in the graph") from err
nx._clear_cache(self)
| (self, u, v) |
30,138 | networkx.classes.graph | remove_edges_from | Remove all edges specified in ebunch.
Parameters
----------
ebunch: list or container of edge tuples
Each edge given in the list or container will be removed
from the graph. The edges can be:
- 2-tuples (u, v) edge between u and v.
- 3-tuples (u, v, k) where k is ignored.
See Also
--------
remove_edge : remove a single edge
Notes
-----
Will fail silently if an edge in ebunch is not in the graph.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> ebunch = [(1, 2), (2, 3)]
>>> G.remove_edges_from(ebunch)
| def remove_edges_from(self, ebunch):
"""Remove all edges specified in ebunch.
Parameters
----------
ebunch: list or container of edge tuples
Each edge given in the list or container will be removed
from the graph. The edges can be:
- 2-tuples (u, v) edge between u and v.
- 3-tuples (u, v, k) where k is ignored.
See Also
--------
remove_edge : remove a single edge
Notes
-----
Will fail silently if an edge in ebunch is not in the graph.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> ebunch = [(1, 2), (2, 3)]
>>> G.remove_edges_from(ebunch)
"""
adj = self._adj
for e in ebunch:
u, v = e[:2] # ignore edge data if present
if u in adj and v in adj[u]:
del adj[u][v]
if u != v: # self loop needs only one entry removed
del adj[v][u]
nx._clear_cache(self)
| (self, ebunch) |
30,139 | networkx.classes.graph | remove_node | Remove node n.
Removes the node n and all adjacent edges.
Attempting to remove a nonexistent node will raise an exception.
Parameters
----------
n : node
A node in the graph
Raises
------
NetworkXError
If n is not in the graph.
See Also
--------
remove_nodes_from
Examples
--------
>>> G = nx.path_graph(3) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> list(G.edges)
[(0, 1), (1, 2)]
>>> G.remove_node(1)
>>> list(G.edges)
[]
| def remove_node(self, n):
"""Remove node n.
Removes the node n and all adjacent edges.
Attempting to remove a nonexistent node will raise an exception.
Parameters
----------
n : node
A node in the graph
Raises
------
NetworkXError
If n is not in the graph.
See Also
--------
remove_nodes_from
Examples
--------
>>> G = nx.path_graph(3) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> list(G.edges)
[(0, 1), (1, 2)]
>>> G.remove_node(1)
>>> list(G.edges)
[]
"""
adj = self._adj
try:
nbrs = list(adj[n]) # list handles self-loops (allows mutation)
del self._node[n]
except KeyError as err: # NetworkXError if n not in self
raise NetworkXError(f"The node {n} is not in the graph.") from err
for u in nbrs:
del adj[u][n] # remove all edges n-u in graph
del adj[n] # now remove node
nx._clear_cache(self)
| (self, n) |
30,140 | networkx.classes.graph | remove_nodes_from | Remove multiple nodes.
Parameters
----------
nodes : iterable container
A container of nodes (list, dict, set, etc.). If a node
in the container is not in the graph it is silently
ignored.
See Also
--------
remove_node
Notes
-----
When removing nodes from an iterator over the graph you are changing,
a `RuntimeError` will be raised with message:
`RuntimeError: dictionary changed size during iteration`. This
happens when the graph's underlying dictionary is modified during
iteration. To avoid this error, evaluate the iterator into a separate
object, e.g. by using `list(iterator_of_nodes)`, and pass this
object to `G.remove_nodes_from`.
Examples
--------
>>> G = nx.path_graph(3) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> e = list(G.nodes)
>>> e
[0, 1, 2]
>>> G.remove_nodes_from(e)
>>> list(G.nodes)
[]
Evaluate an iterator over a graph if using it to modify the same graph
>>> G = nx.Graph([(0, 1), (1, 2), (3, 4)])
>>> # this command will fail, as the graph's dict is modified during iteration
>>> # G.remove_nodes_from(n for n in G.nodes if n < 2)
>>> # this command will work, since the dictionary underlying graph is not modified
>>> G.remove_nodes_from(list(n for n in G.nodes if n < 2))
| def remove_nodes_from(self, nodes):
"""Remove multiple nodes.
Parameters
----------
nodes : iterable container
A container of nodes (list, dict, set, etc.). If a node
in the container is not in the graph it is silently
ignored.
See Also
--------
remove_node
Notes
-----
When removing nodes from an iterator over the graph you are changing,
a `RuntimeError` will be raised with message:
`RuntimeError: dictionary changed size during iteration`. This
happens when the graph's underlying dictionary is modified during
iteration. To avoid this error, evaluate the iterator into a separate
object, e.g. by using `list(iterator_of_nodes)`, and pass this
object to `G.remove_nodes_from`.
Examples
--------
>>> G = nx.path_graph(3) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> e = list(G.nodes)
>>> e
[0, 1, 2]
>>> G.remove_nodes_from(e)
>>> list(G.nodes)
[]
Evaluate an iterator over a graph if using it to modify the same graph
>>> G = nx.Graph([(0, 1), (1, 2), (3, 4)])
>>> # this command will fail, as the graph's dict is modified during iteration
>>> # G.remove_nodes_from(n for n in G.nodes if n < 2)
>>> # this command will work, since the dictionary underlying graph is not modified
>>> G.remove_nodes_from(list(n for n in G.nodes if n < 2))
"""
adj = self._adj
for n in nodes:
try:
del self._node[n]
for u in list(adj[n]): # list handles self-loops
del adj[u][n] # (allows mutation of dict in loop)
del adj[n]
except KeyError:
pass
nx._clear_cache(self)
| (self, nodes) |
30,145 | networkx.classes.graph | to_undirected | Returns an undirected copy of the graph.
Parameters
----------
as_view : bool (optional, default=False)
If True return a view of the original undirected graph.
Returns
-------
G : Graph/MultiGraph
A deepcopy of the graph.
See Also
--------
Graph, copy, add_edge, add_edges_from
Notes
-----
This returns a "deepcopy" of the edge, node, and
graph attributes which attempts to completely copy
all of the data and references.
This is in contrast to the similar `G = nx.DiGraph(D)` which returns a
shallow copy of the data.
See the Python copy module for more information on shallow
and deep copies, https://docs.python.org/3/library/copy.html.
Warning: If you have subclassed DiGraph to use dict-like objects
in the data structure, those changes do not transfer to the
Graph created by this method.
Examples
--------
>>> G = nx.path_graph(2) # or MultiGraph, etc
>>> H = G.to_directed()
>>> list(H.edges)
[(0, 1), (1, 0)]
>>> G2 = H.to_undirected()
>>> list(G2.edges)
[(0, 1)]
| def to_undirected(self, as_view=False):
"""Returns an undirected copy of the graph.
Parameters
----------
as_view : bool (optional, default=False)
If True return a view of the original undirected graph.
Returns
-------
G : Graph/MultiGraph
A deepcopy of the graph.
See Also
--------
Graph, copy, add_edge, add_edges_from
Notes
-----
This returns a "deepcopy" of the edge, node, and
graph attributes which attempts to completely copy
all of the data and references.
This is in contrast to the similar `G = nx.DiGraph(D)` which returns a
shallow copy of the data.
See the Python copy module for more information on shallow
and deep copies, https://docs.python.org/3/library/copy.html.
Warning: If you have subclassed DiGraph to use dict-like objects
in the data structure, those changes do not transfer to the
Graph created by this method.
Examples
--------
>>> G = nx.path_graph(2) # or MultiGraph, etc
>>> H = G.to_directed()
>>> list(H.edges)
[(0, 1), (1, 0)]
>>> G2 = H.to_undirected()
>>> list(G2.edges)
[(0, 1)]
"""
graph_class = self.to_undirected_class()
if as_view is True:
return nx.graphviews.generic_graph_view(self, graph_class)
# deepcopy when not a view
G = graph_class()
G.graph.update(deepcopy(self.graph))
G.add_nodes_from((n, deepcopy(d)) for n, d in self._node.items())
G.add_edges_from(
(u, v, deepcopy(d))
for u, nbrs in self._adj.items()
for v, d in nbrs.items()
)
return G
| (self, as_view=False) |
30,148 | networkx.readwrite.graphml | GraphMLReader | Read a GraphML document. Produces NetworkX graph objects. | class GraphMLReader(GraphML):
"""Read a GraphML document. Produces NetworkX graph objects."""
def __init__(self, node_type=str, edge_key_type=int, force_multigraph=False):
self.construct_types()
self.node_type = node_type
self.edge_key_type = edge_key_type
self.multigraph = force_multigraph # If False, test for multiedges
self.edge_ids = {} # dict mapping (u,v) tuples to edge id attributes
def __call__(self, path=None, string=None):
from xml.etree.ElementTree import ElementTree, fromstring
if path is not None:
self.xml = ElementTree(file=path)
elif string is not None:
self.xml = fromstring(string)
else:
raise ValueError("Must specify either 'path' or 'string' as kwarg")
(keys, defaults) = self.find_graphml_keys(self.xml)
for g in self.xml.findall(f"{{{self.NS_GRAPHML}}}graph"):
yield self.make_graph(g, keys, defaults)
def make_graph(self, graph_xml, graphml_keys, defaults, G=None):
# set default graph type
edgedefault = graph_xml.get("edgedefault", None)
if G is None:
if edgedefault == "directed":
G = nx.MultiDiGraph()
else:
G = nx.MultiGraph()
# set defaults for graph attributes
G.graph["node_default"] = {}
G.graph["edge_default"] = {}
for key_id, value in defaults.items():
key_for = graphml_keys[key_id]["for"]
name = graphml_keys[key_id]["name"]
python_type = graphml_keys[key_id]["type"]
if key_for == "node":
G.graph["node_default"].update({name: python_type(value)})
if key_for == "edge":
G.graph["edge_default"].update({name: python_type(value)})
# hyperedges are not supported
hyperedge = graph_xml.find(f"{{{self.NS_GRAPHML}}}hyperedge")
if hyperedge is not None:
raise nx.NetworkXError("GraphML reader doesn't support hyperedges")
# add nodes
for node_xml in graph_xml.findall(f"{{{self.NS_GRAPHML}}}node"):
self.add_node(G, node_xml, graphml_keys, defaults)
# add edges
for edge_xml in graph_xml.findall(f"{{{self.NS_GRAPHML}}}edge"):
self.add_edge(G, edge_xml, graphml_keys)
# add graph data
data = self.decode_data_elements(graphml_keys, graph_xml)
G.graph.update(data)
# switch to Graph or DiGraph if no parallel edges were found
if self.multigraph:
return G
G = nx.DiGraph(G) if G.is_directed() else nx.Graph(G)
# add explicit edge "id" from file as attribute in NX graph.
nx.set_edge_attributes(G, values=self.edge_ids, name="id")
return G
def add_node(self, G, node_xml, graphml_keys, defaults):
"""Add a node to the graph."""
# warn on finding unsupported ports tag
ports = node_xml.find(f"{{{self.NS_GRAPHML}}}port")
if ports is not None:
warnings.warn("GraphML port tag not supported.")
# find the node by id and cast it to the appropriate type
node_id = self.node_type(node_xml.get("id"))
# get data/attributes for node
data = self.decode_data_elements(graphml_keys, node_xml)
G.add_node(node_id, **data)
# get child nodes
if node_xml.attrib.get("yfiles.foldertype") == "group":
graph_xml = node_xml.find(f"{{{self.NS_GRAPHML}}}graph")
self.make_graph(graph_xml, graphml_keys, defaults, G)
def add_edge(self, G, edge_element, graphml_keys):
"""Add an edge to the graph."""
# warn on finding unsupported ports tag
ports = edge_element.find(f"{{{self.NS_GRAPHML}}}port")
if ports is not None:
warnings.warn("GraphML port tag not supported.")
# raise error if we find mixed directed and undirected edges
directed = edge_element.get("directed")
if G.is_directed() and directed == "false":
msg = "directed=false edge found in directed graph."
raise nx.NetworkXError(msg)
if (not G.is_directed()) and directed == "true":
msg = "directed=true edge found in undirected graph."
raise nx.NetworkXError(msg)
source = self.node_type(edge_element.get("source"))
target = self.node_type(edge_element.get("target"))
data = self.decode_data_elements(graphml_keys, edge_element)
# GraphML stores edge ids as an attribute
# NetworkX uses them as keys in multigraphs too if no key
# attribute is specified
edge_id = edge_element.get("id")
if edge_id:
# self.edge_ids is used by `make_graph` method for non-multigraphs
self.edge_ids[source, target] = edge_id
try:
edge_id = self.edge_key_type(edge_id)
except ValueError: # Could not convert.
pass
else:
edge_id = data.get("key")
if G.has_edge(source, target):
# mark this as a multigraph
self.multigraph = True
# Use add_edges_from to avoid error with add_edge when `'key' in data`
# Note there is only one edge here...
G.add_edges_from([(source, target, edge_id, data)])
def decode_data_elements(self, graphml_keys, obj_xml):
"""Use the key information to decode the data XML if present."""
data = {}
for data_element in obj_xml.findall(f"{{{self.NS_GRAPHML}}}data"):
key = data_element.get("key")
try:
data_name = graphml_keys[key]["name"]
data_type = graphml_keys[key]["type"]
except KeyError as err:
raise nx.NetworkXError(f"Bad GraphML data: no key {key}") from err
text = data_element.text
# assume anything with subelements is a yfiles extension
if text is not None and len(list(data_element)) == 0:
if data_type == bool:
# Ignore cases.
# http://docs.oracle.com/javase/6/docs/api/java/lang/
# Boolean.html#parseBoolean%28java.lang.String%29
data[data_name] = self.convert_bool[text.lower()]
else:
data[data_name] = data_type(text)
elif len(list(data_element)) > 0:
# Assume yfiles as subelements, try to extract node_label
node_label = None
# set GenericNode's configuration as shape type
gn = data_element.find(f"{{{self.NS_Y}}}GenericNode")
if gn is not None:
data["shape_type"] = gn.get("configuration")
for node_type in ["GenericNode", "ShapeNode", "SVGNode", "ImageNode"]:
pref = f"{{{self.NS_Y}}}{node_type}/{{{self.NS_Y}}}"
geometry = data_element.find(f"{pref}Geometry")
if geometry is not None:
data["x"] = geometry.get("x")
data["y"] = geometry.get("y")
if node_label is None:
node_label = data_element.find(f"{pref}NodeLabel")
shape = data_element.find(f"{pref}Shape")
if shape is not None:
data["shape_type"] = shape.get("type")
if node_label is not None:
data["label"] = node_label.text
# check all the different types of edges available in yEd.
for edge_type in [
"PolyLineEdge",
"SplineEdge",
"QuadCurveEdge",
"BezierEdge",
"ArcEdge",
]:
pref = f"{{{self.NS_Y}}}{edge_type}/{{{self.NS_Y}}}"
edge_label = data_element.find(f"{pref}EdgeLabel")
if edge_label is not None:
break
if edge_label is not None:
data["label"] = edge_label.text
elif text is None:
data[data_name] = ""
return data
def find_graphml_keys(self, graph_element):
"""Extracts all the keys and key defaults from the xml."""
graphml_keys = {}
graphml_key_defaults = {}
for k in graph_element.findall(f"{{{self.NS_GRAPHML}}}key"):
attr_id = k.get("id")
attr_type = k.get("attr.type")
attr_name = k.get("attr.name")
yfiles_type = k.get("yfiles.type")
if yfiles_type is not None:
attr_name = yfiles_type
attr_type = "yfiles"
if attr_type is None:
attr_type = "string"
warnings.warn(f"No key type for id {attr_id}. Using string")
if attr_name is None:
raise nx.NetworkXError(f"Unknown key for id {attr_id}.")
graphml_keys[attr_id] = {
"name": attr_name,
"type": self.python_type[attr_type],
"for": k.get("for"),
}
# check for "default" sub-element of key element
default = k.find(f"{{{self.NS_GRAPHML}}}default")
if default is not None:
# Handle default values identically to data element values
python_type = graphml_keys[attr_id]["type"]
if python_type == bool:
graphml_key_defaults[attr_id] = self.convert_bool[
default.text.lower()
]
else:
graphml_key_defaults[attr_id] = python_type(default.text)
return graphml_keys, graphml_key_defaults
| (node_type=<class 'str'>, edge_key_type=<class 'int'>, force_multigraph=False) |
30,149 | networkx.readwrite.graphml | __call__ | null | def __call__(self, path=None, string=None):
from xml.etree.ElementTree import ElementTree, fromstring
if path is not None:
self.xml = ElementTree(file=path)
elif string is not None:
self.xml = fromstring(string)
else:
raise ValueError("Must specify either 'path' or 'string' as kwarg")
(keys, defaults) = self.find_graphml_keys(self.xml)
for g in self.xml.findall(f"{{{self.NS_GRAPHML}}}graph"):
yield self.make_graph(g, keys, defaults)
| (self, path=None, string=None) |
30,150 | networkx.readwrite.graphml | __init__ | null | def __init__(self, node_type=str, edge_key_type=int, force_multigraph=False):
self.construct_types()
self.node_type = node_type
self.edge_key_type = edge_key_type
self.multigraph = force_multigraph # If False, test for multiedges
self.edge_ids = {} # dict mapping (u,v) tuples to edge id attributes
| (self, node_type=<class 'str'>, edge_key_type=<class 'int'>, force_multigraph=False) |
30,151 | networkx.readwrite.graphml | add_edge | Add an edge to the graph. | def add_edge(self, G, edge_element, graphml_keys):
"""Add an edge to the graph."""
# warn on finding unsupported ports tag
ports = edge_element.find(f"{{{self.NS_GRAPHML}}}port")
if ports is not None:
warnings.warn("GraphML port tag not supported.")
# raise error if we find mixed directed and undirected edges
directed = edge_element.get("directed")
if G.is_directed() and directed == "false":
msg = "directed=false edge found in directed graph."
raise nx.NetworkXError(msg)
if (not G.is_directed()) and directed == "true":
msg = "directed=true edge found in undirected graph."
raise nx.NetworkXError(msg)
source = self.node_type(edge_element.get("source"))
target = self.node_type(edge_element.get("target"))
data = self.decode_data_elements(graphml_keys, edge_element)
# GraphML stores edge ids as an attribute
# NetworkX uses them as keys in multigraphs too if no key
# attribute is specified
edge_id = edge_element.get("id")
if edge_id:
# self.edge_ids is used by `make_graph` method for non-multigraphs
self.edge_ids[source, target] = edge_id
try:
edge_id = self.edge_key_type(edge_id)
except ValueError: # Could not convert.
pass
else:
edge_id = data.get("key")
if G.has_edge(source, target):
# mark this as a multigraph
self.multigraph = True
# Use add_edges_from to avoid error with add_edge when `'key' in data`
# Note there is only one edge here...
G.add_edges_from([(source, target, edge_id, data)])
| (self, G, edge_element, graphml_keys) |
30,152 | networkx.readwrite.graphml | add_node | Add a node to the graph. | def add_node(self, G, node_xml, graphml_keys, defaults):
"""Add a node to the graph."""
# warn on finding unsupported ports tag
ports = node_xml.find(f"{{{self.NS_GRAPHML}}}port")
if ports is not None:
warnings.warn("GraphML port tag not supported.")
# find the node by id and cast it to the appropriate type
node_id = self.node_type(node_xml.get("id"))
# get data/attributes for node
data = self.decode_data_elements(graphml_keys, node_xml)
G.add_node(node_id, **data)
# get child nodes
if node_xml.attrib.get("yfiles.foldertype") == "group":
graph_xml = node_xml.find(f"{{{self.NS_GRAPHML}}}graph")
self.make_graph(graph_xml, graphml_keys, defaults, G)
| (self, G, node_xml, graphml_keys, defaults) |
30,153 | networkx.readwrite.graphml | construct_types | null | def construct_types(self):
types = [
(int, "integer"), # for Gephi GraphML bug
(str, "yfiles"),
(str, "string"),
(int, "int"),
(int, "long"),
(float, "float"),
(float, "double"),
(bool, "boolean"),
]
# These additions to types allow writing numpy types
try:
import numpy as np
except:
pass
else:
# prepend so that python types are created upon read (last entry wins)
types = [
(np.float64, "float"),
(np.float32, "float"),
(np.float16, "float"),
(np.int_, "int"),
(np.int8, "int"),
(np.int16, "int"),
(np.int32, "int"),
(np.int64, "int"),
(np.uint8, "int"),
(np.uint16, "int"),
(np.uint32, "int"),
(np.uint64, "int"),
(np.int_, "int"),
(np.intc, "int"),
(np.intp, "int"),
] + types
self.xml_type = dict(types)
self.python_type = dict(reversed(a) for a in types)
| (self) |
30,154 | networkx.readwrite.graphml | decode_data_elements | Use the key information to decode the data XML if present. | def decode_data_elements(self, graphml_keys, obj_xml):
"""Use the key information to decode the data XML if present."""
data = {}
for data_element in obj_xml.findall(f"{{{self.NS_GRAPHML}}}data"):
key = data_element.get("key")
try:
data_name = graphml_keys[key]["name"]
data_type = graphml_keys[key]["type"]
except KeyError as err:
raise nx.NetworkXError(f"Bad GraphML data: no key {key}") from err
text = data_element.text
# assume anything with subelements is a yfiles extension
if text is not None and len(list(data_element)) == 0:
if data_type == bool:
# Ignore cases.
# http://docs.oracle.com/javase/6/docs/api/java/lang/
# Boolean.html#parseBoolean%28java.lang.String%29
data[data_name] = self.convert_bool[text.lower()]
else:
data[data_name] = data_type(text)
elif len(list(data_element)) > 0:
# Assume yfiles as subelements, try to extract node_label
node_label = None
# set GenericNode's configuration as shape type
gn = data_element.find(f"{{{self.NS_Y}}}GenericNode")
if gn is not None:
data["shape_type"] = gn.get("configuration")
for node_type in ["GenericNode", "ShapeNode", "SVGNode", "ImageNode"]:
pref = f"{{{self.NS_Y}}}{node_type}/{{{self.NS_Y}}}"
geometry = data_element.find(f"{pref}Geometry")
if geometry is not None:
data["x"] = geometry.get("x")
data["y"] = geometry.get("y")
if node_label is None:
node_label = data_element.find(f"{pref}NodeLabel")
shape = data_element.find(f"{pref}Shape")
if shape is not None:
data["shape_type"] = shape.get("type")
if node_label is not None:
data["label"] = node_label.text
# check all the different types of edges available in yEd.
for edge_type in [
"PolyLineEdge",
"SplineEdge",
"QuadCurveEdge",
"BezierEdge",
"ArcEdge",
]:
pref = f"{{{self.NS_Y}}}{edge_type}/{{{self.NS_Y}}}"
edge_label = data_element.find(f"{pref}EdgeLabel")
if edge_label is not None:
break
if edge_label is not None:
data["label"] = edge_label.text
elif text is None:
data[data_name] = ""
return data
| (self, graphml_keys, obj_xml) |
30,155 | networkx.readwrite.graphml | find_graphml_keys | Extracts all the keys and key defaults from the xml. | def find_graphml_keys(self, graph_element):
"""Extracts all the keys and key defaults from the xml."""
graphml_keys = {}
graphml_key_defaults = {}
for k in graph_element.findall(f"{{{self.NS_GRAPHML}}}key"):
attr_id = k.get("id")
attr_type = k.get("attr.type")
attr_name = k.get("attr.name")
yfiles_type = k.get("yfiles.type")
if yfiles_type is not None:
attr_name = yfiles_type
attr_type = "yfiles"
if attr_type is None:
attr_type = "string"
warnings.warn(f"No key type for id {attr_id}. Using string")
if attr_name is None:
raise nx.NetworkXError(f"Unknown key for id {attr_id}.")
graphml_keys[attr_id] = {
"name": attr_name,
"type": self.python_type[attr_type],
"for": k.get("for"),
}
# check for "default" sub-element of key element
default = k.find(f"{{{self.NS_GRAPHML}}}default")
if default is not None:
# Handle default values identically to data element values
python_type = graphml_keys[attr_id]["type"]
if python_type == bool:
graphml_key_defaults[attr_id] = self.convert_bool[
default.text.lower()
]
else:
graphml_key_defaults[attr_id] = python_type(default.text)
return graphml_keys, graphml_key_defaults
| (self, graph_element) |
30,156 | networkx.readwrite.graphml | get_xml_type | Wrapper around the xml_type dict that raises a more informative
exception message when a user attempts to use data of a type not
supported by GraphML. | def get_xml_type(self, key):
"""Wrapper around the xml_type dict that raises a more informative
exception message when a user attempts to use data of a type not
supported by GraphML."""
try:
return self.xml_type[key]
except KeyError as err:
raise TypeError(
f"GraphML does not support type {key} as data values."
) from err
| (self, key) |
30,157 | networkx.readwrite.graphml | make_graph | null | def make_graph(self, graph_xml, graphml_keys, defaults, G=None):
# set default graph type
edgedefault = graph_xml.get("edgedefault", None)
if G is None:
if edgedefault == "directed":
G = nx.MultiDiGraph()
else:
G = nx.MultiGraph()
# set defaults for graph attributes
G.graph["node_default"] = {}
G.graph["edge_default"] = {}
for key_id, value in defaults.items():
key_for = graphml_keys[key_id]["for"]
name = graphml_keys[key_id]["name"]
python_type = graphml_keys[key_id]["type"]
if key_for == "node":
G.graph["node_default"].update({name: python_type(value)})
if key_for == "edge":
G.graph["edge_default"].update({name: python_type(value)})
# hyperedges are not supported
hyperedge = graph_xml.find(f"{{{self.NS_GRAPHML}}}hyperedge")
if hyperedge is not None:
raise nx.NetworkXError("GraphML reader doesn't support hyperedges")
# add nodes
for node_xml in graph_xml.findall(f"{{{self.NS_GRAPHML}}}node"):
self.add_node(G, node_xml, graphml_keys, defaults)
# add edges
for edge_xml in graph_xml.findall(f"{{{self.NS_GRAPHML}}}edge"):
self.add_edge(G, edge_xml, graphml_keys)
# add graph data
data = self.decode_data_elements(graphml_keys, graph_xml)
G.graph.update(data)
# switch to Graph or DiGraph if no parallel edges were found
if self.multigraph:
return G
G = nx.DiGraph(G) if G.is_directed() else nx.Graph(G)
# add explicit edge "id" from file as attribute in NX graph.
nx.set_edge_attributes(G, values=self.edge_ids, name="id")
return G
| (self, graph_xml, graphml_keys, defaults, G=None) |
30,158 | networkx.readwrite.graphml | GraphMLWriter | null | class GraphMLWriter(GraphML):
def __init__(
self,
graph=None,
encoding="utf-8",
prettyprint=True,
infer_numeric_types=False,
named_key_ids=False,
edge_id_from_attribute=None,
):
self.construct_types()
from xml.etree.ElementTree import Element
self.myElement = Element
self.infer_numeric_types = infer_numeric_types
self.prettyprint = prettyprint
self.named_key_ids = named_key_ids
self.edge_id_from_attribute = edge_id_from_attribute
self.encoding = encoding
self.xml = self.myElement(
"graphml",
{
"xmlns": self.NS_GRAPHML,
"xmlns:xsi": self.NS_XSI,
"xsi:schemaLocation": self.SCHEMALOCATION,
},
)
self.keys = {}
self.attributes = defaultdict(list)
self.attribute_types = defaultdict(set)
if graph is not None:
self.add_graph_element(graph)
def __str__(self):
from xml.etree.ElementTree import tostring
if self.prettyprint:
self.indent(self.xml)
s = tostring(self.xml).decode(self.encoding)
return s
def attr_type(self, name, scope, value):
"""Infer the attribute type of data named name. Currently this only
supports inference of numeric types.
If self.infer_numeric_types is false, type is used. Otherwise, pick the
most general of types found across all values with name and scope. This
means edges with data named 'weight' are treated separately from nodes
with data named 'weight'.
"""
if self.infer_numeric_types:
types = self.attribute_types[(name, scope)]
if len(types) > 1:
types = {self.get_xml_type(t) for t in types}
if "string" in types:
return str
elif "float" in types or "double" in types:
return float
else:
return int
else:
return list(types)[0]
else:
return type(value)
def get_key(self, name, attr_type, scope, default):
keys_key = (name, attr_type, scope)
try:
return self.keys[keys_key]
except KeyError:
if self.named_key_ids:
new_id = name
else:
new_id = f"d{len(list(self.keys))}"
self.keys[keys_key] = new_id
key_kwargs = {
"id": new_id,
"for": scope,
"attr.name": name,
"attr.type": attr_type,
}
key_element = self.myElement("key", **key_kwargs)
# add subelement for data default value if present
if default is not None:
default_element = self.myElement("default")
default_element.text = str(default)
key_element.append(default_element)
self.xml.insert(0, key_element)
return new_id
def add_data(self, name, element_type, value, scope="all", default=None):
"""
Make a data element for an edge or a node. Keep a log of the
type in the keys table.
"""
if element_type not in self.xml_type:
raise nx.NetworkXError(
f"GraphML writer does not support {element_type} as data values."
)
keyid = self.get_key(name, self.get_xml_type(element_type), scope, default)
data_element = self.myElement("data", key=keyid)
data_element.text = str(value)
return data_element
def add_attributes(self, scope, xml_obj, data, default):
"""Appends attribute data to edges or nodes, and stores type information
to be added later. See add_graph_element.
"""
for k, v in data.items():
self.attribute_types[(str(k), scope)].add(type(v))
self.attributes[xml_obj].append([k, v, scope, default.get(k)])
def add_nodes(self, G, graph_element):
default = G.graph.get("node_default", {})
for node, data in G.nodes(data=True):
node_element = self.myElement("node", id=str(node))
self.add_attributes("node", node_element, data, default)
graph_element.append(node_element)
def add_edges(self, G, graph_element):
if G.is_multigraph():
for u, v, key, data in G.edges(data=True, keys=True):
edge_element = self.myElement(
"edge",
source=str(u),
target=str(v),
id=str(data.get(self.edge_id_from_attribute))
if self.edge_id_from_attribute
and self.edge_id_from_attribute in data
else str(key),
)
default = G.graph.get("edge_default", {})
self.add_attributes("edge", edge_element, data, default)
graph_element.append(edge_element)
else:
for u, v, data in G.edges(data=True):
if self.edge_id_from_attribute and self.edge_id_from_attribute in data:
# select attribute to be edge id
edge_element = self.myElement(
"edge",
source=str(u),
target=str(v),
id=str(data.get(self.edge_id_from_attribute)),
)
else:
# default: no edge id
edge_element = self.myElement("edge", source=str(u), target=str(v))
default = G.graph.get("edge_default", {})
self.add_attributes("edge", edge_element, data, default)
graph_element.append(edge_element)
def add_graph_element(self, G):
"""
Serialize graph G in GraphML to the stream.
"""
if G.is_directed():
default_edge_type = "directed"
else:
default_edge_type = "undirected"
graphid = G.graph.pop("id", None)
if graphid is None:
graph_element = self.myElement("graph", edgedefault=default_edge_type)
else:
graph_element = self.myElement(
"graph", edgedefault=default_edge_type, id=graphid
)
default = {}
data = {
k: v
for (k, v) in G.graph.items()
if k not in ["node_default", "edge_default"]
}
self.add_attributes("graph", graph_element, data, default)
self.add_nodes(G, graph_element)
self.add_edges(G, graph_element)
# self.attributes contains a mapping from XML Objects to a list of
# data that needs to be added to them.
# We postpone processing in order to do type inference/generalization.
# See self.attr_type
for xml_obj, data in self.attributes.items():
for k, v, scope, default in data:
xml_obj.append(
self.add_data(
str(k), self.attr_type(k, scope, v), str(v), scope, default
)
)
self.xml.append(graph_element)
def add_graphs(self, graph_list):
"""Add many graphs to this GraphML document."""
for G in graph_list:
self.add_graph_element(G)
def dump(self, stream):
from xml.etree.ElementTree import ElementTree
if self.prettyprint:
self.indent(self.xml)
document = ElementTree(self.xml)
document.write(stream, encoding=self.encoding, xml_declaration=True)
def indent(self, elem, level=0):
# in-place prettyprint formatter
i = "\n" + level * " "
if len(elem):
if not elem.text or not elem.text.strip():
elem.text = i + " "
if not elem.tail or not elem.tail.strip():
elem.tail = i
for elem in elem:
self.indent(elem, level + 1)
if not elem.tail or not elem.tail.strip():
elem.tail = i
else:
if level and (not elem.tail or not elem.tail.strip()):
elem.tail = i
| (graph=None, encoding='utf-8', prettyprint=True, infer_numeric_types=False, named_key_ids=False, edge_id_from_attribute=None) |
30,159 | networkx.readwrite.graphml | __init__ | null | def __init__(
self,
graph=None,
encoding="utf-8",
prettyprint=True,
infer_numeric_types=False,
named_key_ids=False,
edge_id_from_attribute=None,
):
self.construct_types()
from xml.etree.ElementTree import Element
self.myElement = Element
self.infer_numeric_types = infer_numeric_types
self.prettyprint = prettyprint
self.named_key_ids = named_key_ids
self.edge_id_from_attribute = edge_id_from_attribute
self.encoding = encoding
self.xml = self.myElement(
"graphml",
{
"xmlns": self.NS_GRAPHML,
"xmlns:xsi": self.NS_XSI,
"xsi:schemaLocation": self.SCHEMALOCATION,
},
)
self.keys = {}
self.attributes = defaultdict(list)
self.attribute_types = defaultdict(set)
if graph is not None:
self.add_graph_element(graph)
| (self, graph=None, encoding='utf-8', prettyprint=True, infer_numeric_types=False, named_key_ids=False, edge_id_from_attribute=None) |
30,160 | networkx.readwrite.graphml | __str__ | null | def __str__(self):
from xml.etree.ElementTree import tostring
if self.prettyprint:
self.indent(self.xml)
s = tostring(self.xml).decode(self.encoding)
return s
| (self) |
30,161 | networkx.readwrite.graphml | add_attributes | Appends attribute data to edges or nodes, and stores type information
to be added later. See add_graph_element.
| def add_attributes(self, scope, xml_obj, data, default):
"""Appends attribute data to edges or nodes, and stores type information
to be added later. See add_graph_element.
"""
for k, v in data.items():
self.attribute_types[(str(k), scope)].add(type(v))
self.attributes[xml_obj].append([k, v, scope, default.get(k)])
| (self, scope, xml_obj, data, default) |
30,162 | networkx.readwrite.graphml | add_data |
Make a data element for an edge or a node. Keep a log of the
type in the keys table.
| def add_data(self, name, element_type, value, scope="all", default=None):
"""
Make a data element for an edge or a node. Keep a log of the
type in the keys table.
"""
if element_type not in self.xml_type:
raise nx.NetworkXError(
f"GraphML writer does not support {element_type} as data values."
)
keyid = self.get_key(name, self.get_xml_type(element_type), scope, default)
data_element = self.myElement("data", key=keyid)
data_element.text = str(value)
return data_element
| (self, name, element_type, value, scope='all', default=None) |
30,163 | networkx.readwrite.graphml | add_edges | null | def add_edges(self, G, graph_element):
if G.is_multigraph():
for u, v, key, data in G.edges(data=True, keys=True):
edge_element = self.myElement(
"edge",
source=str(u),
target=str(v),
id=str(data.get(self.edge_id_from_attribute))
if self.edge_id_from_attribute
and self.edge_id_from_attribute in data
else str(key),
)
default = G.graph.get("edge_default", {})
self.add_attributes("edge", edge_element, data, default)
graph_element.append(edge_element)
else:
for u, v, data in G.edges(data=True):
if self.edge_id_from_attribute and self.edge_id_from_attribute in data:
# select attribute to be edge id
edge_element = self.myElement(
"edge",
source=str(u),
target=str(v),
id=str(data.get(self.edge_id_from_attribute)),
)
else:
# default: no edge id
edge_element = self.myElement("edge", source=str(u), target=str(v))
default = G.graph.get("edge_default", {})
self.add_attributes("edge", edge_element, data, default)
graph_element.append(edge_element)
| (self, G, graph_element) |
30,164 | networkx.readwrite.graphml | add_graph_element |
Serialize graph G in GraphML to the stream.
| def add_graph_element(self, G):
"""
Serialize graph G in GraphML to the stream.
"""
if G.is_directed():
default_edge_type = "directed"
else:
default_edge_type = "undirected"
graphid = G.graph.pop("id", None)
if graphid is None:
graph_element = self.myElement("graph", edgedefault=default_edge_type)
else:
graph_element = self.myElement(
"graph", edgedefault=default_edge_type, id=graphid
)
default = {}
data = {
k: v
for (k, v) in G.graph.items()
if k not in ["node_default", "edge_default"]
}
self.add_attributes("graph", graph_element, data, default)
self.add_nodes(G, graph_element)
self.add_edges(G, graph_element)
# self.attributes contains a mapping from XML Objects to a list of
# data that needs to be added to them.
# We postpone processing in order to do type inference/generalization.
# See self.attr_type
for xml_obj, data in self.attributes.items():
for k, v, scope, default in data:
xml_obj.append(
self.add_data(
str(k), self.attr_type(k, scope, v), str(v), scope, default
)
)
self.xml.append(graph_element)
| (self, G) |
30,165 | networkx.readwrite.graphml | add_graphs | Add many graphs to this GraphML document. | def add_graphs(self, graph_list):
"""Add many graphs to this GraphML document."""
for G in graph_list:
self.add_graph_element(G)
| (self, graph_list) |
30,166 | networkx.readwrite.graphml | add_nodes | null | def add_nodes(self, G, graph_element):
default = G.graph.get("node_default", {})
for node, data in G.nodes(data=True):
node_element = self.myElement("node", id=str(node))
self.add_attributes("node", node_element, data, default)
graph_element.append(node_element)
| (self, G, graph_element) |
30,167 | networkx.readwrite.graphml | attr_type | Infer the attribute type of data named name. Currently this only
supports inference of numeric types.
If self.infer_numeric_types is false, type is used. Otherwise, pick the
most general of types found across all values with name and scope. This
means edges with data named 'weight' are treated separately from nodes
with data named 'weight'.
| def attr_type(self, name, scope, value):
"""Infer the attribute type of data named name. Currently this only
supports inference of numeric types.
If self.infer_numeric_types is false, type is used. Otherwise, pick the
most general of types found across all values with name and scope. This
means edges with data named 'weight' are treated separately from nodes
with data named 'weight'.
"""
if self.infer_numeric_types:
types = self.attribute_types[(name, scope)]
if len(types) > 1:
types = {self.get_xml_type(t) for t in types}
if "string" in types:
return str
elif "float" in types or "double" in types:
return float
else:
return int
else:
return list(types)[0]
else:
return type(value)
| (self, name, scope, value) |
30,169 | networkx.readwrite.graphml | dump | null | def dump(self, stream):
from xml.etree.ElementTree import ElementTree
if self.prettyprint:
self.indent(self.xml)
document = ElementTree(self.xml)
document.write(stream, encoding=self.encoding, xml_declaration=True)
| (self, stream) |
30,170 | networkx.readwrite.graphml | get_key | null | def get_key(self, name, attr_type, scope, default):
keys_key = (name, attr_type, scope)
try:
return self.keys[keys_key]
except KeyError:
if self.named_key_ids:
new_id = name
else:
new_id = f"d{len(list(self.keys))}"
self.keys[keys_key] = new_id
key_kwargs = {
"id": new_id,
"for": scope,
"attr.name": name,
"attr.type": attr_type,
}
key_element = self.myElement("key", **key_kwargs)
# add subelement for data default value if present
if default is not None:
default_element = self.myElement("default")
default_element.text = str(default)
key_element.append(default_element)
self.xml.insert(0, key_element)
return new_id
| (self, name, attr_type, scope, default) |
30,172 | networkx.readwrite.graphml | indent | null | def indent(self, elem, level=0):
# in-place prettyprint formatter
i = "\n" + level * " "
if len(elem):
if not elem.text or not elem.text.strip():
elem.text = i + " "
if not elem.tail or not elem.tail.strip():
elem.tail = i
for elem in elem:
self.indent(elem, level + 1)
if not elem.tail or not elem.tail.strip():
elem.tail = i
else:
if level and (not elem.tail or not elem.tail.strip()):
elem.tail = i
| (self, elem, level=0) |
30,173 | networkx.exception | HasACycle | Raised if a graph has a cycle when an algorithm expects that it
will have no cycles.
| class HasACycle(NetworkXException):
"""Raised if a graph has a cycle when an algorithm expects that it
will have no cycles.
"""
| null |
30,174 | networkx.generators.small | LCF_graph |
Return the cubic graph specified in LCF notation.
LCF (Lederberg-Coxeter-Fruchte) notation[1]_ is a compressed
notation used in the generation of various cubic Hamiltonian
graphs of high symmetry. See, for example, `dodecahedral_graph`,
`desargues_graph`, `heawood_graph` and `pappus_graph`.
Nodes are drawn from ``range(n)``. Each node ``n_i`` is connected with
node ``n_i + shift % n`` where ``shift`` is given by cycling through
the input `shift_list` `repeat` s times.
Parameters
----------
n : int
The starting graph is the `n`-cycle with nodes ``0, ..., n-1``.
The null graph is returned if `n` < 1.
shift_list : list
A list of integer shifts mod `n`, ``[s1, s2, .., sk]``
repeats : int
Integer specifying the number of times that shifts in `shift_list`
are successively applied to each current node in the n-cycle
to generate an edge between ``n_current`` and ``n_current + shift mod n``.
Returns
-------
G : Graph
A graph instance created from the specified LCF notation.
Examples
--------
The utility graph $K_{3,3}$
>>> G = nx.LCF_graph(6, [3, -3], 3)
>>> G.edges()
EdgeView([(0, 1), (0, 5), (0, 3), (1, 2), (1, 4), (2, 3), (2, 5), (3, 4), (4, 5)])
The Heawood graph:
>>> G = nx.LCF_graph(14, [5, -5], 7)
>>> nx.is_isomorphic(G, nx.heawood_graph())
True
References
----------
.. [1] https://en.wikipedia.org/wiki/LCF_notation
| def sedgewick_maze_graph(create_using=None):
"""
Return a small maze with a cycle.
This is the maze used in Sedgewick, 3rd Edition, Part 5, Graph
Algorithms, Chapter 18, e.g. Figure 18.2 and following [1]_.
Nodes are numbered 0,..,7
Parameters
----------
create_using : NetworkX graph constructor, optional (default=nx.Graph)
Graph type to create. If graph instance, then cleared before populated.
Returns
-------
G : networkx Graph
Small maze with a cycle
References
----------
.. [1] Figure 18.2, Chapter 18, Graph Algorithms (3rd Ed), Sedgewick
"""
G = empty_graph(0, create_using)
G.add_nodes_from(range(8))
G.add_edges_from([[0, 2], [0, 7], [0, 5]])
G.add_edges_from([[1, 7], [2, 6]])
G.add_edges_from([[3, 4], [3, 5]])
G.add_edges_from([[4, 5], [4, 7], [4, 6]])
G.name = "Sedgewick Maze"
return G
| (n, shift_list, repeats, create_using=None, *, backend=None, **backend_kwargs) |
30,175 | networkx.generators.community | LFR_benchmark_graph | Returns the LFR benchmark graph.
This algorithm proceeds as follows:
1) Find a degree sequence with a power law distribution, and minimum
value ``min_degree``, which has approximate average degree
``average_degree``. This is accomplished by either
a) specifying ``min_degree`` and not ``average_degree``,
b) specifying ``average_degree`` and not ``min_degree``, in which
case a suitable minimum degree will be found.
``max_degree`` can also be specified, otherwise it will be set to
``n``. Each node *u* will have $\mu \mathrm{deg}(u)$ edges
joining it to nodes in communities other than its own and $(1 -
\mu) \mathrm{deg}(u)$ edges joining it to nodes in its own
community.
2) Generate community sizes according to a power law distribution
with exponent ``tau2``. If ``min_community`` and
``max_community`` are not specified they will be selected to be
``min_degree`` and ``max_degree``, respectively. Community sizes
are generated until the sum of their sizes equals ``n``.
3) Each node will be randomly assigned a community with the
condition that the community is large enough for the node's
intra-community degree, $(1 - \mu) \mathrm{deg}(u)$ as
described in step 2. If a community grows too large, a random node
will be selected for reassignment to a new community, until all
nodes have been assigned a community.
4) Each node *u* then adds $(1 - \mu) \mathrm{deg}(u)$
intra-community edges and $\mu \mathrm{deg}(u)$ inter-community
edges.
Parameters
----------
n : int
Number of nodes in the created graph.
tau1 : float
Power law exponent for the degree distribution of the created
graph. This value must be strictly greater than one.
tau2 : float
Power law exponent for the community size distribution in the
created graph. This value must be strictly greater than one.
mu : float
Fraction of inter-community edges incident to each node. This
value must be in the interval [0, 1].
average_degree : float
Desired average degree of nodes in the created graph. This value
must be in the interval [0, *n*]. Exactly one of this and
``min_degree`` must be specified, otherwise a
:exc:`NetworkXError` is raised.
min_degree : int
Minimum degree of nodes in the created graph. This value must be
in the interval [0, *n*]. Exactly one of this and
``average_degree`` must be specified, otherwise a
:exc:`NetworkXError` is raised.
max_degree : int
Maximum degree of nodes in the created graph. If not specified,
this is set to ``n``, the total number of nodes in the graph.
min_community : int
Minimum size of communities in the graph. If not specified, this
is set to ``min_degree``.
max_community : int
Maximum size of communities in the graph. If not specified, this
is set to ``n``, the total number of nodes in the graph.
tol : float
Tolerance when comparing floats, specifically when comparing
average degree values.
max_iters : int
Maximum number of iterations to try to create the community sizes,
degree distribution, and community affiliations.
seed : integer, random_state, or None (default)
Indicator of random number generation state.
See :ref:`Randomness<randomness>`.
Returns
-------
G : NetworkX graph
The LFR benchmark graph generated according to the specified
parameters.
Each node in the graph has a node attribute ``'community'`` that
stores the community (that is, the set of nodes) that includes
it.
Raises
------
NetworkXError
If any of the parameters do not meet their upper and lower bounds:
- ``tau1`` and ``tau2`` must be strictly greater than 1.
- ``mu`` must be in [0, 1].
- ``max_degree`` must be in {1, ..., *n*}.
- ``min_community`` and ``max_community`` must be in {0, ...,
*n*}.
If not exactly one of ``average_degree`` and ``min_degree`` is
specified.
If ``min_degree`` is not specified and a suitable ``min_degree``
cannot be found.
ExceededMaxIterations
If a valid degree sequence cannot be created within
``max_iters`` number of iterations.
If a valid set of community sizes cannot be created within
``max_iters`` number of iterations.
If a valid community assignment cannot be created within ``10 *
n * max_iters`` number of iterations.
Examples
--------
Basic usage::
>>> from networkx.generators.community import LFR_benchmark_graph
>>> n = 250
>>> tau1 = 3
>>> tau2 = 1.5
>>> mu = 0.1
>>> G = LFR_benchmark_graph(
... n, tau1, tau2, mu, average_degree=5, min_community=20, seed=10
... )
Continuing the example above, you can get the communities from the
node attributes of the graph::
>>> communities = {frozenset(G.nodes[v]["community"]) for v in G}
Notes
-----
This algorithm differs slightly from the original way it was
presented in [1].
1) Rather than connecting the graph via a configuration model then
rewiring to match the intra-community and inter-community
degrees, we do this wiring explicitly at the end, which should be
equivalent.
2) The code posted on the author's website [2] calculates the random
power law distributed variables and their average using
continuous approximations, whereas we use the discrete
distributions here as both degree and community size are
discrete.
Though the authors describe the algorithm as quite robust, testing
during development indicates that a somewhat narrower parameter set
is likely to successfully produce a graph. Some suggestions have
been provided in the event of exceptions.
References
----------
.. [1] "Benchmark graphs for testing community detection algorithms",
Andrea Lancichinetti, Santo Fortunato, and Filippo Radicchi,
Phys. Rev. E 78, 046110 2008
.. [2] https://www.santofortunato.net/resources
| def _generate_communities(degree_seq, community_sizes, mu, max_iters, seed):
"""Returns a list of sets, each of which represents a community.
``degree_seq`` is the degree sequence that must be met by the
graph.
``community_sizes`` is the community size distribution that must be
met by the generated list of sets.
``mu`` is a float in the interval [0, 1] indicating the fraction of
intra-community edges incident to each node.
``max_iters`` is the number of times to try to add a node to a
community. This must be greater than the length of
``degree_seq``, otherwise this function will always fail. If
the number of iterations exceeds this value,
:exc:`~networkx.exception.ExceededMaxIterations` is raised.
seed : integer, random_state, or None (default)
Indicator of random number generation state.
See :ref:`Randomness<randomness>`.
The communities returned by this are sets of integers in the set {0,
..., *n* - 1}, where *n* is the length of ``degree_seq``.
"""
# This assumes the nodes in the graph will be natural numbers.
result = [set() for _ in community_sizes]
n = len(degree_seq)
free = list(range(n))
for i in range(max_iters):
v = free.pop()
c = seed.choice(range(len(community_sizes)))
# s = int(degree_seq[v] * (1 - mu) + 0.5)
s = round(degree_seq[v] * (1 - mu))
# If the community is large enough, add the node to the chosen
# community. Otherwise, return it to the list of unaffiliated
# nodes.
if s < community_sizes[c]:
result[c].add(v)
else:
free.append(v)
# If the community is too big, remove a node from it.
if len(result[c]) > community_sizes[c]:
free.append(result[c].pop())
if not free:
return result
msg = "Could not assign communities; try increasing min_community"
raise nx.ExceededMaxIterations(msg)
| (n, tau1, tau2, mu, average_degree=None, min_degree=None, max_degree=None, min_community=None, max_community=None, tol=1e-07, max_iters=500, seed=None, *, backend=None, **backend_kwargs) |
30,176 | networkx.classes.multidigraph | MultiDiGraph | A directed graph class that can store multiedges.
Multiedges are multiple edges between two nodes. Each edge
can hold optional data or attributes.
A MultiDiGraph holds directed edges. Self loops are allowed.
Nodes can be arbitrary (hashable) Python objects with optional
key/value attributes. By convention `None` is not used as a node.
Edges are represented as links between nodes with optional
key/value attributes.
Parameters
----------
incoming_graph_data : input graph (optional, default: None)
Data to initialize graph. If None (default) an empty
graph is created. The data can be any format that is supported
by the to_networkx_graph() function, currently including edge list,
dict of dicts, dict of lists, NetworkX graph, 2D NumPy array, SciPy
sparse matrix, or PyGraphviz graph.
multigraph_input : bool or None (default None)
Note: Only used when `incoming_graph_data` is a dict.
If True, `incoming_graph_data` is assumed to be a
dict-of-dict-of-dict-of-dict structure keyed by
node to neighbor to edge keys to edge data for multi-edges.
A NetworkXError is raised if this is not the case.
If False, :func:`to_networkx_graph` is used to try to determine
the dict's graph data structure as either a dict-of-dict-of-dict
keyed by node to neighbor to edge data, or a dict-of-iterable
keyed by node to neighbors.
If None, the treatment for True is tried, but if it fails,
the treatment for False is tried.
attr : keyword arguments, optional (default= no attributes)
Attributes to add to graph as key=value pairs.
See Also
--------
Graph
DiGraph
MultiGraph
Examples
--------
Create an empty graph structure (a "null graph") with no nodes and
no edges.
>>> G = nx.MultiDiGraph()
G can be grown in several ways.
**Nodes:**
Add one node at a time:
>>> G.add_node(1)
Add the nodes from any container (a list, dict, set or
even the lines from a file or the nodes from another graph).
>>> G.add_nodes_from([2, 3])
>>> G.add_nodes_from(range(100, 110))
>>> H = nx.path_graph(10)
>>> G.add_nodes_from(H)
In addition to strings and integers any hashable Python object
(except None) can represent a node, e.g. a customized node object,
or even another Graph.
>>> G.add_node(H)
**Edges:**
G can also be grown by adding edges.
Add one edge,
>>> key = G.add_edge(1, 2)
a list of edges,
>>> keys = G.add_edges_from([(1, 2), (1, 3)])
or a collection of edges,
>>> keys = G.add_edges_from(H.edges)
If some edges connect nodes not yet in the graph, the nodes
are added automatically. If an edge already exists, an additional
edge is created and stored using a key to identify the edge.
By default the key is the lowest unused integer.
>>> keys = G.add_edges_from([(4, 5, dict(route=282)), (4, 5, dict(route=37))])
>>> G[4]
AdjacencyView({5: {0: {}, 1: {'route': 282}, 2: {'route': 37}}})
**Attributes:**
Each graph, node, and edge can hold key/value attribute pairs
in an associated attribute dictionary (the keys must be hashable).
By default these are empty, but can be added or changed using
add_edge, add_node or direct manipulation of the attribute
dictionaries named graph, node and edge respectively.
>>> G = nx.MultiDiGraph(day="Friday")
>>> G.graph
{'day': 'Friday'}
Add node attributes using add_node(), add_nodes_from() or G.nodes
>>> G.add_node(1, time="5pm")
>>> G.add_nodes_from([3], time="2pm")
>>> G.nodes[1]
{'time': '5pm'}
>>> G.nodes[1]["room"] = 714
>>> del G.nodes[1]["room"] # remove attribute
>>> list(G.nodes(data=True))
[(1, {'time': '5pm'}), (3, {'time': '2pm'})]
Add edge attributes using add_edge(), add_edges_from(), subscript
notation, or G.edges.
>>> key = G.add_edge(1, 2, weight=4.7)
>>> keys = G.add_edges_from([(3, 4), (4, 5)], color="red")
>>> keys = G.add_edges_from([(1, 2, {"color": "blue"}), (2, 3, {"weight": 8})])
>>> G[1][2][0]["weight"] = 4.7
>>> G.edges[1, 2, 0]["weight"] = 4
Warning: we protect the graph data structure by making `G.edges[1,
2, 0]` a read-only dict-like structure. However, you can assign to
attributes in e.g. `G.edges[1, 2, 0]`. Thus, use 2 sets of brackets
to add/change data attributes: `G.edges[1, 2, 0]['weight'] = 4`
(for multigraphs the edge key is required: `MG.edges[u, v,
key][name] = value`).
**Shortcuts:**
Many common graph features allow python syntax to speed reporting.
>>> 1 in G # check if node in graph
True
>>> [n for n in G if n < 3] # iterate through nodes
[1, 2]
>>> len(G) # number of nodes in graph
5
>>> G[1] # adjacency dict-like view mapping neighbor -> edge key -> edge attributes
AdjacencyView({2: {0: {'weight': 4}, 1: {'color': 'blue'}}})
Often the best way to traverse all edges of a graph is via the neighbors.
The neighbors are available as an adjacency-view `G.adj` object or via
the method `G.adjacency()`.
>>> for n, nbrsdict in G.adjacency():
... for nbr, keydict in nbrsdict.items():
... for key, eattr in keydict.items():
... if "weight" in eattr:
... # Do something useful with the edges
... pass
But the edges() method is often more convenient:
>>> for u, v, keys, weight in G.edges(data="weight", keys=True):
... if weight is not None:
... # Do something useful with the edges
... pass
**Reporting:**
Simple graph information is obtained using methods and object-attributes.
Reporting usually provides views instead of containers to reduce memory
usage. The views update as the graph is updated similarly to dict-views.
The objects `nodes`, `edges` and `adj` provide access to data attributes
via lookup (e.g. `nodes[n]`, `edges[u, v, k]`, `adj[u][v]`) and iteration
(e.g. `nodes.items()`, `nodes.data('color')`,
`nodes.data('color', default='blue')` and similarly for `edges`)
Views exist for `nodes`, `edges`, `neighbors()`/`adj` and `degree`.
For details on these and other miscellaneous methods, see below.
**Subclasses (Advanced):**
The MultiDiGraph class uses a dict-of-dict-of-dict-of-dict structure.
The outer dict (node_dict) holds adjacency information keyed by node.
The next dict (adjlist_dict) represents the adjacency information
and holds edge_key dicts keyed by neighbor. The edge_key dict holds
each edge_attr dict keyed by edge key. The inner dict
(edge_attr_dict) represents the edge data and holds edge attribute
values keyed by attribute names.
Each of these four dicts in the dict-of-dict-of-dict-of-dict
structure can be replaced by a user defined dict-like object.
In general, the dict-like features should be maintained but
extra features can be added. To replace one of the dicts create
a new graph class by changing the class(!) variable holding the
factory for that dict-like structure. The variable names are
node_dict_factory, node_attr_dict_factory, adjlist_inner_dict_factory,
adjlist_outer_dict_factory, edge_key_dict_factory, edge_attr_dict_factory
and graph_attr_dict_factory.
node_dict_factory : function, (default: dict)
Factory function to be used to create the dict containing node
attributes, keyed by node id.
It should require no arguments and return a dict-like object
node_attr_dict_factory: function, (default: dict)
Factory function to be used to create the node attribute
dict which holds attribute values keyed by attribute name.
It should require no arguments and return a dict-like object
adjlist_outer_dict_factory : function, (default: dict)
Factory function to be used to create the outer-most dict
in the data structure that holds adjacency info keyed by node.
It should require no arguments and return a dict-like object.
adjlist_inner_dict_factory : function, (default: dict)
Factory function to be used to create the adjacency list
dict which holds multiedge key dicts keyed by neighbor.
It should require no arguments and return a dict-like object.
edge_key_dict_factory : function, (default: dict)
Factory function to be used to create the edge key dict
which holds edge data keyed by edge key.
It should require no arguments and return a dict-like object.
edge_attr_dict_factory : function, (default: dict)
Factory function to be used to create the edge attribute
dict which holds attribute values keyed by attribute name.
It should require no arguments and return a dict-like object.
graph_attr_dict_factory : function, (default: dict)
Factory function to be used to create the graph attribute
dict which holds attribute values keyed by attribute name.
It should require no arguments and return a dict-like object.
Typically, if your extension doesn't impact the data structure all
methods will inherited without issue except: `to_directed/to_undirected`.
By default these methods create a DiGraph/Graph class and you probably
want them to create your extension of a DiGraph/Graph. To facilitate
this we define two class variables that you can set in your subclass.
to_directed_class : callable, (default: DiGraph or MultiDiGraph)
Class to create a new graph structure in the `to_directed` method.
If `None`, a NetworkX class (DiGraph or MultiDiGraph) is used.
to_undirected_class : callable, (default: Graph or MultiGraph)
Class to create a new graph structure in the `to_undirected` method.
If `None`, a NetworkX class (Graph or MultiGraph) is used.
**Subclassing Example**
Create a low memory graph class that effectively disallows edge
attributes by using a single attribute dict for all edges.
This reduces the memory used, but you lose edge attributes.
>>> class ThinGraph(nx.Graph):
... all_edge_dict = {"weight": 1}
...
... def single_edge_dict(self):
... return self.all_edge_dict
...
... edge_attr_dict_factory = single_edge_dict
>>> G = ThinGraph()
>>> G.add_edge(2, 1)
>>> G[2][1]
{'weight': 1}
>>> G.add_edge(2, 2)
>>> G[2][1] is G[2][2]
True
| class MultiDiGraph(MultiGraph, DiGraph):
"""A directed graph class that can store multiedges.
Multiedges are multiple edges between two nodes. Each edge
can hold optional data or attributes.
A MultiDiGraph holds directed edges. Self loops are allowed.
Nodes can be arbitrary (hashable) Python objects with optional
key/value attributes. By convention `None` is not used as a node.
Edges are represented as links between nodes with optional
key/value attributes.
Parameters
----------
incoming_graph_data : input graph (optional, default: None)
Data to initialize graph. If None (default) an empty
graph is created. The data can be any format that is supported
by the to_networkx_graph() function, currently including edge list,
dict of dicts, dict of lists, NetworkX graph, 2D NumPy array, SciPy
sparse matrix, or PyGraphviz graph.
multigraph_input : bool or None (default None)
Note: Only used when `incoming_graph_data` is a dict.
If True, `incoming_graph_data` is assumed to be a
dict-of-dict-of-dict-of-dict structure keyed by
node to neighbor to edge keys to edge data for multi-edges.
A NetworkXError is raised if this is not the case.
If False, :func:`to_networkx_graph` is used to try to determine
the dict's graph data structure as either a dict-of-dict-of-dict
keyed by node to neighbor to edge data, or a dict-of-iterable
keyed by node to neighbors.
If None, the treatment for True is tried, but if it fails,
the treatment for False is tried.
attr : keyword arguments, optional (default= no attributes)
Attributes to add to graph as key=value pairs.
See Also
--------
Graph
DiGraph
MultiGraph
Examples
--------
Create an empty graph structure (a "null graph") with no nodes and
no edges.
>>> G = nx.MultiDiGraph()
G can be grown in several ways.
**Nodes:**
Add one node at a time:
>>> G.add_node(1)
Add the nodes from any container (a list, dict, set or
even the lines from a file or the nodes from another graph).
>>> G.add_nodes_from([2, 3])
>>> G.add_nodes_from(range(100, 110))
>>> H = nx.path_graph(10)
>>> G.add_nodes_from(H)
In addition to strings and integers any hashable Python object
(except None) can represent a node, e.g. a customized node object,
or even another Graph.
>>> G.add_node(H)
**Edges:**
G can also be grown by adding edges.
Add one edge,
>>> key = G.add_edge(1, 2)
a list of edges,
>>> keys = G.add_edges_from([(1, 2), (1, 3)])
or a collection of edges,
>>> keys = G.add_edges_from(H.edges)
If some edges connect nodes not yet in the graph, the nodes
are added automatically. If an edge already exists, an additional
edge is created and stored using a key to identify the edge.
By default the key is the lowest unused integer.
>>> keys = G.add_edges_from([(4, 5, dict(route=282)), (4, 5, dict(route=37))])
>>> G[4]
AdjacencyView({5: {0: {}, 1: {'route': 282}, 2: {'route': 37}}})
**Attributes:**
Each graph, node, and edge can hold key/value attribute pairs
in an associated attribute dictionary (the keys must be hashable).
By default these are empty, but can be added or changed using
add_edge, add_node or direct manipulation of the attribute
dictionaries named graph, node and edge respectively.
>>> G = nx.MultiDiGraph(day="Friday")
>>> G.graph
{'day': 'Friday'}
Add node attributes using add_node(), add_nodes_from() or G.nodes
>>> G.add_node(1, time="5pm")
>>> G.add_nodes_from([3], time="2pm")
>>> G.nodes[1]
{'time': '5pm'}
>>> G.nodes[1]["room"] = 714
>>> del G.nodes[1]["room"] # remove attribute
>>> list(G.nodes(data=True))
[(1, {'time': '5pm'}), (3, {'time': '2pm'})]
Add edge attributes using add_edge(), add_edges_from(), subscript
notation, or G.edges.
>>> key = G.add_edge(1, 2, weight=4.7)
>>> keys = G.add_edges_from([(3, 4), (4, 5)], color="red")
>>> keys = G.add_edges_from([(1, 2, {"color": "blue"}), (2, 3, {"weight": 8})])
>>> G[1][2][0]["weight"] = 4.7
>>> G.edges[1, 2, 0]["weight"] = 4
Warning: we protect the graph data structure by making `G.edges[1,
2, 0]` a read-only dict-like structure. However, you can assign to
attributes in e.g. `G.edges[1, 2, 0]`. Thus, use 2 sets of brackets
to add/change data attributes: `G.edges[1, 2, 0]['weight'] = 4`
(for multigraphs the edge key is required: `MG.edges[u, v,
key][name] = value`).
**Shortcuts:**
Many common graph features allow python syntax to speed reporting.
>>> 1 in G # check if node in graph
True
>>> [n for n in G if n < 3] # iterate through nodes
[1, 2]
>>> len(G) # number of nodes in graph
5
>>> G[1] # adjacency dict-like view mapping neighbor -> edge key -> edge attributes
AdjacencyView({2: {0: {'weight': 4}, 1: {'color': 'blue'}}})
Often the best way to traverse all edges of a graph is via the neighbors.
The neighbors are available as an adjacency-view `G.adj` object or via
the method `G.adjacency()`.
>>> for n, nbrsdict in G.adjacency():
... for nbr, keydict in nbrsdict.items():
... for key, eattr in keydict.items():
... if "weight" in eattr:
... # Do something useful with the edges
... pass
But the edges() method is often more convenient:
>>> for u, v, keys, weight in G.edges(data="weight", keys=True):
... if weight is not None:
... # Do something useful with the edges
... pass
**Reporting:**
Simple graph information is obtained using methods and object-attributes.
Reporting usually provides views instead of containers to reduce memory
usage. The views update as the graph is updated similarly to dict-views.
The objects `nodes`, `edges` and `adj` provide access to data attributes
via lookup (e.g. `nodes[n]`, `edges[u, v, k]`, `adj[u][v]`) and iteration
(e.g. `nodes.items()`, `nodes.data('color')`,
`nodes.data('color', default='blue')` and similarly for `edges`)
Views exist for `nodes`, `edges`, `neighbors()`/`adj` and `degree`.
For details on these and other miscellaneous methods, see below.
**Subclasses (Advanced):**
The MultiDiGraph class uses a dict-of-dict-of-dict-of-dict structure.
The outer dict (node_dict) holds adjacency information keyed by node.
The next dict (adjlist_dict) represents the adjacency information
and holds edge_key dicts keyed by neighbor. The edge_key dict holds
each edge_attr dict keyed by edge key. The inner dict
(edge_attr_dict) represents the edge data and holds edge attribute
values keyed by attribute names.
Each of these four dicts in the dict-of-dict-of-dict-of-dict
structure can be replaced by a user defined dict-like object.
In general, the dict-like features should be maintained but
extra features can be added. To replace one of the dicts create
a new graph class by changing the class(!) variable holding the
factory for that dict-like structure. The variable names are
node_dict_factory, node_attr_dict_factory, adjlist_inner_dict_factory,
adjlist_outer_dict_factory, edge_key_dict_factory, edge_attr_dict_factory
and graph_attr_dict_factory.
node_dict_factory : function, (default: dict)
Factory function to be used to create the dict containing node
attributes, keyed by node id.
It should require no arguments and return a dict-like object
node_attr_dict_factory: function, (default: dict)
Factory function to be used to create the node attribute
dict which holds attribute values keyed by attribute name.
It should require no arguments and return a dict-like object
adjlist_outer_dict_factory : function, (default: dict)
Factory function to be used to create the outer-most dict
in the data structure that holds adjacency info keyed by node.
It should require no arguments and return a dict-like object.
adjlist_inner_dict_factory : function, (default: dict)
Factory function to be used to create the adjacency list
dict which holds multiedge key dicts keyed by neighbor.
It should require no arguments and return a dict-like object.
edge_key_dict_factory : function, (default: dict)
Factory function to be used to create the edge key dict
which holds edge data keyed by edge key.
It should require no arguments and return a dict-like object.
edge_attr_dict_factory : function, (default: dict)
Factory function to be used to create the edge attribute
dict which holds attribute values keyed by attribute name.
It should require no arguments and return a dict-like object.
graph_attr_dict_factory : function, (default: dict)
Factory function to be used to create the graph attribute
dict which holds attribute values keyed by attribute name.
It should require no arguments and return a dict-like object.
Typically, if your extension doesn't impact the data structure all
methods will inherited without issue except: `to_directed/to_undirected`.
By default these methods create a DiGraph/Graph class and you probably
want them to create your extension of a DiGraph/Graph. To facilitate
this we define two class variables that you can set in your subclass.
to_directed_class : callable, (default: DiGraph or MultiDiGraph)
Class to create a new graph structure in the `to_directed` method.
If `None`, a NetworkX class (DiGraph or MultiDiGraph) is used.
to_undirected_class : callable, (default: Graph or MultiGraph)
Class to create a new graph structure in the `to_undirected` method.
If `None`, a NetworkX class (Graph or MultiGraph) is used.
**Subclassing Example**
Create a low memory graph class that effectively disallows edge
attributes by using a single attribute dict for all edges.
This reduces the memory used, but you lose edge attributes.
>>> class ThinGraph(nx.Graph):
... all_edge_dict = {"weight": 1}
...
... def single_edge_dict(self):
... return self.all_edge_dict
...
... edge_attr_dict_factory = single_edge_dict
>>> G = ThinGraph()
>>> G.add_edge(2, 1)
>>> G[2][1]
{'weight': 1}
>>> G.add_edge(2, 2)
>>> G[2][1] is G[2][2]
True
"""
# node_dict_factory = dict # already assigned in Graph
# adjlist_outer_dict_factory = dict
# adjlist_inner_dict_factory = dict
edge_key_dict_factory = dict
# edge_attr_dict_factory = dict
def __init__(self, incoming_graph_data=None, multigraph_input=None, **attr):
"""Initialize a graph with edges, name, or graph attributes.
Parameters
----------
incoming_graph_data : input graph
Data to initialize graph. If incoming_graph_data=None (default)
an empty graph is created. The data can be an edge list, or any
NetworkX graph object. If the corresponding optional Python
packages are installed the data can also be a 2D NumPy array, a
SciPy sparse array, or a PyGraphviz graph.
multigraph_input : bool or None (default None)
Note: Only used when `incoming_graph_data` is a dict.
If True, `incoming_graph_data` is assumed to be a
dict-of-dict-of-dict-of-dict structure keyed by
node to neighbor to edge keys to edge data for multi-edges.
A NetworkXError is raised if this is not the case.
If False, :func:`to_networkx_graph` is used to try to determine
the dict's graph data structure as either a dict-of-dict-of-dict
keyed by node to neighbor to edge data, or a dict-of-iterable
keyed by node to neighbors.
If None, the treatment for True is tried, but if it fails,
the treatment for False is tried.
attr : keyword arguments, optional (default= no attributes)
Attributes to add to graph as key=value pairs.
See Also
--------
convert
Examples
--------
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G = nx.Graph(name="my graph")
>>> e = [(1, 2), (2, 3), (3, 4)] # list of edges
>>> G = nx.Graph(e)
Arbitrary graph attribute pairs (key=value) may be assigned
>>> G = nx.Graph(e, day="Friday")
>>> G.graph
{'day': 'Friday'}
"""
# multigraph_input can be None/True/False. So check "is not False"
if isinstance(incoming_graph_data, dict) and multigraph_input is not False:
DiGraph.__init__(self)
try:
convert.from_dict_of_dicts(
incoming_graph_data, create_using=self, multigraph_input=True
)
self.graph.update(attr)
except Exception as err:
if multigraph_input is True:
raise nx.NetworkXError(
f"converting multigraph_input raised:\n{type(err)}: {err}"
)
DiGraph.__init__(self, incoming_graph_data, **attr)
else:
DiGraph.__init__(self, incoming_graph_data, **attr)
@cached_property
def adj(self):
"""Graph adjacency object holding the neighbors of each node.
This object is a read-only dict-like structure with node keys
and neighbor-dict values. The neighbor-dict is keyed by neighbor
to the edgekey-dict. So `G.adj[3][2][0]['color'] = 'blue'` sets
the color of the edge `(3, 2, 0)` to `"blue"`.
Iterating over G.adj behaves like a dict. Useful idioms include
`for nbr, datadict in G.adj[n].items():`.
The neighbor information is also provided by subscripting the graph.
So `for nbr, foovalue in G[node].data('foo', default=1):` works.
For directed graphs, `G.adj` holds outgoing (successor) info.
"""
return MultiAdjacencyView(self._succ)
@cached_property
def succ(self):
"""Graph adjacency object holding the successors of each node.
This object is a read-only dict-like structure with node keys
and neighbor-dict values. The neighbor-dict is keyed by neighbor
to the edgekey-dict. So `G.adj[3][2][0]['color'] = 'blue'` sets
the color of the edge `(3, 2, 0)` to `"blue"`.
Iterating over G.adj behaves like a dict. Useful idioms include
`for nbr, datadict in G.adj[n].items():`.
The neighbor information is also provided by subscripting the graph.
So `for nbr, foovalue in G[node].data('foo', default=1):` works.
For directed graphs, `G.succ` is identical to `G.adj`.
"""
return MultiAdjacencyView(self._succ)
@cached_property
def pred(self):
"""Graph adjacency object holding the predecessors of each node.
This object is a read-only dict-like structure with node keys
and neighbor-dict values. The neighbor-dict is keyed by neighbor
to the edgekey-dict. So `G.adj[3][2][0]['color'] = 'blue'` sets
the color of the edge `(3, 2, 0)` to `"blue"`.
Iterating over G.adj behaves like a dict. Useful idioms include
`for nbr, datadict in G.adj[n].items():`.
"""
return MultiAdjacencyView(self._pred)
def add_edge(self, u_for_edge, v_for_edge, key=None, **attr):
"""Add an edge between u and v.
The nodes u and v will be automatically added if they are
not already in the graph.
Edge attributes can be specified with keywords or by directly
accessing the edge's attribute dictionary. See examples below.
Parameters
----------
u_for_edge, v_for_edge : nodes
Nodes can be, for example, strings or numbers.
Nodes must be hashable (and not None) Python objects.
key : hashable identifier, optional (default=lowest unused integer)
Used to distinguish multiedges between a pair of nodes.
attr : keyword arguments, optional
Edge data (or labels or objects) can be assigned using
keyword arguments.
Returns
-------
The edge key assigned to the edge.
See Also
--------
add_edges_from : add a collection of edges
Notes
-----
To replace/update edge data, use the optional key argument
to identify a unique edge. Otherwise a new edge will be created.
NetworkX algorithms designed for weighted graphs cannot use
multigraphs directly because it is not clear how to handle
multiedge weights. Convert to Graph using edge attribute
'weight' to enable weighted graph algorithms.
Default keys are generated using the method `new_edge_key()`.
This method can be overridden by subclassing the base class and
providing a custom `new_edge_key()` method.
Examples
--------
The following all add the edge e=(1, 2) to graph G:
>>> G = nx.MultiDiGraph()
>>> e = (1, 2)
>>> key = G.add_edge(1, 2) # explicit two-node form
>>> G.add_edge(*e) # single edge as tuple of two nodes
1
>>> G.add_edges_from([(1, 2)]) # add edges from iterable container
[2]
Associate data to edges using keywords:
>>> key = G.add_edge(1, 2, weight=3)
>>> key = G.add_edge(1, 2, key=0, weight=4) # update data for key=0
>>> key = G.add_edge(1, 3, weight=7, capacity=15, length=342.7)
For non-string attribute keys, use subscript notation.
>>> ekey = G.add_edge(1, 2)
>>> G[1][2][0].update({0: 5})
>>> G.edges[1, 2, 0].update({0: 5})
"""
u, v = u_for_edge, v_for_edge
# add nodes
if u not in self._succ:
if u is None:
raise ValueError("None cannot be a node")
self._succ[u] = self.adjlist_inner_dict_factory()
self._pred[u] = self.adjlist_inner_dict_factory()
self._node[u] = self.node_attr_dict_factory()
if v not in self._succ:
if v is None:
raise ValueError("None cannot be a node")
self._succ[v] = self.adjlist_inner_dict_factory()
self._pred[v] = self.adjlist_inner_dict_factory()
self._node[v] = self.node_attr_dict_factory()
if key is None:
key = self.new_edge_key(u, v)
if v in self._succ[u]:
keydict = self._adj[u][v]
datadict = keydict.get(key, self.edge_attr_dict_factory())
datadict.update(attr)
keydict[key] = datadict
else:
# selfloops work this way without special treatment
datadict = self.edge_attr_dict_factory()
datadict.update(attr)
keydict = self.edge_key_dict_factory()
keydict[key] = datadict
self._succ[u][v] = keydict
self._pred[v][u] = keydict
nx._clear_cache(self)
return key
def remove_edge(self, u, v, key=None):
"""Remove an edge between u and v.
Parameters
----------
u, v : nodes
Remove an edge between nodes u and v.
key : hashable identifier, optional (default=None)
Used to distinguish multiple edges between a pair of nodes.
If None, remove a single edge between u and v. If there are
multiple edges, removes the last edge added in terms of
insertion order.
Raises
------
NetworkXError
If there is not an edge between u and v, or
if there is no edge with the specified key.
See Also
--------
remove_edges_from : remove a collection of edges
Examples
--------
>>> G = nx.MultiDiGraph()
>>> nx.add_path(G, [0, 1, 2, 3])
>>> G.remove_edge(0, 1)
>>> e = (1, 2)
>>> G.remove_edge(*e) # unpacks e from an edge tuple
For multiple edges
>>> G = nx.MultiDiGraph()
>>> G.add_edges_from([(1, 2), (1, 2), (1, 2)]) # key_list returned
[0, 1, 2]
When ``key=None`` (the default), edges are removed in the opposite
order that they were added:
>>> G.remove_edge(1, 2)
>>> G.edges(keys=True)
OutMultiEdgeView([(1, 2, 0), (1, 2, 1)])
For edges with keys
>>> G = nx.MultiDiGraph()
>>> G.add_edge(1, 2, key="first")
'first'
>>> G.add_edge(1, 2, key="second")
'second'
>>> G.remove_edge(1, 2, key="first")
>>> G.edges(keys=True)
OutMultiEdgeView([(1, 2, 'second')])
"""
try:
d = self._adj[u][v]
except KeyError as err:
raise NetworkXError(f"The edge {u}-{v} is not in the graph.") from err
# remove the edge with specified data
if key is None:
d.popitem()
else:
try:
del d[key]
except KeyError as err:
msg = f"The edge {u}-{v} with key {key} is not in the graph."
raise NetworkXError(msg) from err
if len(d) == 0:
# remove the key entries if last edge
del self._succ[u][v]
del self._pred[v][u]
nx._clear_cache(self)
@cached_property
def edges(self):
"""An OutMultiEdgeView of the Graph as G.edges or G.edges().
edges(self, nbunch=None, data=False, keys=False, default=None)
The OutMultiEdgeView provides set-like operations on the edge-tuples
as well as edge attribute lookup. When called, it also provides
an EdgeDataView object which allows control of access to edge
attributes (but does not provide set-like operations).
Hence, ``G.edges[u, v, k]['color']`` provides the value of the color
attribute for the edge from ``u`` to ``v`` with key ``k`` while
``for (u, v, k, c) in G.edges(data='color', default='red', keys=True):``
iterates through all the edges yielding the color attribute with
default `'red'` if no color attribute exists.
Edges are returned as tuples with optional data and keys
in the order (node, neighbor, key, data). If ``keys=True`` is not
provided, the tuples will just be (node, neighbor, data), but
multiple tuples with the same node and neighbor will be
generated when multiple edges between two nodes exist.
Parameters
----------
nbunch : single node, container, or all nodes (default= all nodes)
The view will only report edges from these nodes.
data : string or bool, optional (default=False)
The edge attribute returned in 3-tuple (u, v, ddict[data]).
If True, return edge attribute dict in 3-tuple (u, v, ddict).
If False, return 2-tuple (u, v).
keys : bool, optional (default=False)
If True, return edge keys with each edge, creating (u, v, k,
d) tuples when data is also requested (the default) and (u,
v, k) tuples when data is not requested.
default : value, optional (default=None)
Value used for edges that don't have the requested attribute.
Only relevant if data is not True or False.
Returns
-------
edges : OutMultiEdgeView
A view of edge attributes, usually it iterates over (u, v)
(u, v, k) or (u, v, k, d) tuples of edges, but can also be
used for attribute lookup as ``edges[u, v, k]['foo']``.
Notes
-----
Nodes in nbunch that are not in the graph will be (quietly) ignored.
For directed graphs this returns the out-edges.
Examples
--------
>>> G = nx.MultiDiGraph()
>>> nx.add_path(G, [0, 1, 2])
>>> key = G.add_edge(2, 3, weight=5)
>>> key2 = G.add_edge(1, 2) # second edge between these nodes
>>> [e for e in G.edges()]
[(0, 1), (1, 2), (1, 2), (2, 3)]
>>> list(G.edges(data=True)) # default data is {} (empty dict)
[(0, 1, {}), (1, 2, {}), (1, 2, {}), (2, 3, {'weight': 5})]
>>> list(G.edges(data="weight", default=1))
[(0, 1, 1), (1, 2, 1), (1, 2, 1), (2, 3, 5)]
>>> list(G.edges(keys=True)) # default keys are integers
[(0, 1, 0), (1, 2, 0), (1, 2, 1), (2, 3, 0)]
>>> list(G.edges(data=True, keys=True))
[(0, 1, 0, {}), (1, 2, 0, {}), (1, 2, 1, {}), (2, 3, 0, {'weight': 5})]
>>> list(G.edges(data="weight", default=1, keys=True))
[(0, 1, 0, 1), (1, 2, 0, 1), (1, 2, 1, 1), (2, 3, 0, 5)]
>>> list(G.edges([0, 2]))
[(0, 1), (2, 3)]
>>> list(G.edges(0))
[(0, 1)]
>>> list(G.edges(1))
[(1, 2), (1, 2)]
See Also
--------
in_edges, out_edges
"""
return OutMultiEdgeView(self)
# alias out_edges to edges
@cached_property
def out_edges(self):
return OutMultiEdgeView(self)
out_edges.__doc__ = edges.__doc__
@cached_property
def in_edges(self):
"""A view of the in edges of the graph as G.in_edges or G.in_edges().
in_edges(self, nbunch=None, data=False, keys=False, default=None)
Parameters
----------
nbunch : single node, container, or all nodes (default= all nodes)
The view will only report edges incident to these nodes.
data : string or bool, optional (default=False)
The edge attribute returned in 3-tuple (u, v, ddict[data]).
If True, return edge attribute dict in 3-tuple (u, v, ddict).
If False, return 2-tuple (u, v).
keys : bool, optional (default=False)
If True, return edge keys with each edge, creating 3-tuples
(u, v, k) or with data, 4-tuples (u, v, k, d).
default : value, optional (default=None)
Value used for edges that don't have the requested attribute.
Only relevant if data is not True or False.
Returns
-------
in_edges : InMultiEdgeView or InMultiEdgeDataView
A view of edge attributes, usually it iterates over (u, v)
or (u, v, k) or (u, v, k, d) tuples of edges, but can also be
used for attribute lookup as `edges[u, v, k]['foo']`.
See Also
--------
edges
"""
return InMultiEdgeView(self)
@cached_property
def degree(self):
"""A DegreeView for the Graph as G.degree or G.degree().
The node degree is the number of edges adjacent to the node.
The weighted node degree is the sum of the edge weights for
edges incident to that node.
This object provides an iterator for (node, degree) as well as
lookup for the degree for a single node.
Parameters
----------
nbunch : single node, container, or all nodes (default= all nodes)
The view will only report edges incident to these nodes.
weight : string or None, optional (default=None)
The name of an edge attribute that holds the numerical value used
as a weight. If None, then each edge has weight 1.
The degree is the sum of the edge weights adjacent to the node.
Returns
-------
DiMultiDegreeView or int
If multiple nodes are requested (the default), returns a `DiMultiDegreeView`
mapping nodes to their degree.
If a single node is requested, returns the degree of the node as an integer.
See Also
--------
out_degree, in_degree
Examples
--------
>>> G = nx.MultiDiGraph()
>>> nx.add_path(G, [0, 1, 2, 3])
>>> G.degree(0) # node 0 with degree 1
1
>>> list(G.degree([0, 1, 2]))
[(0, 1), (1, 2), (2, 2)]
>>> G.add_edge(0, 1) # parallel edge
1
>>> list(G.degree([0, 1, 2])) # parallel edges are counted
[(0, 2), (1, 3), (2, 2)]
"""
return DiMultiDegreeView(self)
@cached_property
def in_degree(self):
"""A DegreeView for (node, in_degree) or in_degree for single node.
The node in-degree is the number of edges pointing into the node.
The weighted node degree is the sum of the edge weights for
edges incident to that node.
This object provides an iterator for (node, degree) as well as
lookup for the degree for a single node.
Parameters
----------
nbunch : single node, container, or all nodes (default= all nodes)
The view will only report edges incident to these nodes.
weight : string or None, optional (default=None)
The edge attribute that holds the numerical value used
as a weight. If None, then each edge has weight 1.
The degree is the sum of the edge weights adjacent to the node.
Returns
-------
If a single node is requested
deg : int
Degree of the node
OR if multiple nodes are requested
nd_iter : iterator
The iterator returns two-tuples of (node, in-degree).
See Also
--------
degree, out_degree
Examples
--------
>>> G = nx.MultiDiGraph()
>>> nx.add_path(G, [0, 1, 2, 3])
>>> G.in_degree(0) # node 0 with degree 0
0
>>> list(G.in_degree([0, 1, 2]))
[(0, 0), (1, 1), (2, 1)]
>>> G.add_edge(0, 1) # parallel edge
1
>>> list(G.in_degree([0, 1, 2])) # parallel edges counted
[(0, 0), (1, 2), (2, 1)]
"""
return InMultiDegreeView(self)
@cached_property
def out_degree(self):
"""Returns an iterator for (node, out-degree) or out-degree for single node.
out_degree(self, nbunch=None, weight=None)
The node out-degree is the number of edges pointing out of the node.
This function returns the out-degree for a single node or an iterator
for a bunch of nodes or if nothing is passed as argument.
Parameters
----------
nbunch : single node, container, or all nodes (default= all nodes)
The view will only report edges incident to these nodes.
weight : string or None, optional (default=None)
The edge attribute that holds the numerical value used
as a weight. If None, then each edge has weight 1.
The degree is the sum of the edge weights.
Returns
-------
If a single node is requested
deg : int
Degree of the node
OR if multiple nodes are requested
nd_iter : iterator
The iterator returns two-tuples of (node, out-degree).
See Also
--------
degree, in_degree
Examples
--------
>>> G = nx.MultiDiGraph()
>>> nx.add_path(G, [0, 1, 2, 3])
>>> G.out_degree(0) # node 0 with degree 1
1
>>> list(G.out_degree([0, 1, 2]))
[(0, 1), (1, 1), (2, 1)]
>>> G.add_edge(0, 1) # parallel edge
1
>>> list(G.out_degree([0, 1, 2])) # counts parallel edges
[(0, 2), (1, 1), (2, 1)]
"""
return OutMultiDegreeView(self)
def is_multigraph(self):
"""Returns True if graph is a multigraph, False otherwise."""
return True
def is_directed(self):
"""Returns True if graph is directed, False otherwise."""
return True
def to_undirected(self, reciprocal=False, as_view=False):
"""Returns an undirected representation of the digraph.
Parameters
----------
reciprocal : bool (optional)
If True only keep edges that appear in both directions
in the original digraph.
as_view : bool (optional, default=False)
If True return an undirected view of the original directed graph.
Returns
-------
G : MultiGraph
An undirected graph with the same name and nodes and
with edge (u, v, data) if either (u, v, data) or (v, u, data)
is in the digraph. If both edges exist in digraph and
their edge data is different, only one edge is created
with an arbitrary choice of which edge data to use.
You must check and correct for this manually if desired.
See Also
--------
MultiGraph, copy, add_edge, add_edges_from
Notes
-----
This returns a "deepcopy" of the edge, node, and
graph attributes which attempts to completely copy
all of the data and references.
This is in contrast to the similar D=MultiDiGraph(G) which
returns a shallow copy of the data.
See the Python copy module for more information on shallow
and deep copies, https://docs.python.org/3/library/copy.html.
Warning: If you have subclassed MultiDiGraph to use dict-like
objects in the data structure, those changes do not transfer
to the MultiGraph created by this method.
Examples
--------
>>> G = nx.path_graph(2) # or MultiGraph, etc
>>> H = G.to_directed()
>>> list(H.edges)
[(0, 1), (1, 0)]
>>> G2 = H.to_undirected()
>>> list(G2.edges)
[(0, 1)]
"""
graph_class = self.to_undirected_class()
if as_view is True:
return nx.graphviews.generic_graph_view(self, graph_class)
# deepcopy when not a view
G = graph_class()
G.graph.update(deepcopy(self.graph))
G.add_nodes_from((n, deepcopy(d)) for n, d in self._node.items())
if reciprocal is True:
G.add_edges_from(
(u, v, key, deepcopy(data))
for u, nbrs in self._adj.items()
for v, keydict in nbrs.items()
for key, data in keydict.items()
if v in self._pred[u] and key in self._pred[u][v]
)
else:
G.add_edges_from(
(u, v, key, deepcopy(data))
for u, nbrs in self._adj.items()
for v, keydict in nbrs.items()
for key, data in keydict.items()
)
return G
def reverse(self, copy=True):
"""Returns the reverse of the graph.
The reverse is a graph with the same nodes and edges
but with the directions of the edges reversed.
Parameters
----------
copy : bool optional (default=True)
If True, return a new DiGraph holding the reversed edges.
If False, the reverse graph is created using a view of
the original graph.
"""
if copy:
H = self.__class__()
H.graph.update(deepcopy(self.graph))
H.add_nodes_from((n, deepcopy(d)) for n, d in self._node.items())
H.add_edges_from(
(v, u, k, deepcopy(d))
for u, v, k, d in self.edges(keys=True, data=True)
)
return H
return nx.reverse_view(self)
| (incoming_graph_data=None, multigraph_input=None, **attr) |
30,179 | networkx.classes.multidigraph | __init__ | Initialize a graph with edges, name, or graph attributes.
Parameters
----------
incoming_graph_data : input graph
Data to initialize graph. If incoming_graph_data=None (default)
an empty graph is created. The data can be an edge list, or any
NetworkX graph object. If the corresponding optional Python
packages are installed the data can also be a 2D NumPy array, a
SciPy sparse array, or a PyGraphviz graph.
multigraph_input : bool or None (default None)
Note: Only used when `incoming_graph_data` is a dict.
If True, `incoming_graph_data` is assumed to be a
dict-of-dict-of-dict-of-dict structure keyed by
node to neighbor to edge keys to edge data for multi-edges.
A NetworkXError is raised if this is not the case.
If False, :func:`to_networkx_graph` is used to try to determine
the dict's graph data structure as either a dict-of-dict-of-dict
keyed by node to neighbor to edge data, or a dict-of-iterable
keyed by node to neighbors.
If None, the treatment for True is tried, but if it fails,
the treatment for False is tried.
attr : keyword arguments, optional (default= no attributes)
Attributes to add to graph as key=value pairs.
See Also
--------
convert
Examples
--------
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G = nx.Graph(name="my graph")
>>> e = [(1, 2), (2, 3), (3, 4)] # list of edges
>>> G = nx.Graph(e)
Arbitrary graph attribute pairs (key=value) may be assigned
>>> G = nx.Graph(e, day="Friday")
>>> G.graph
{'day': 'Friday'}
| def __init__(self, incoming_graph_data=None, multigraph_input=None, **attr):
"""Initialize a graph with edges, name, or graph attributes.
Parameters
----------
incoming_graph_data : input graph
Data to initialize graph. If incoming_graph_data=None (default)
an empty graph is created. The data can be an edge list, or any
NetworkX graph object. If the corresponding optional Python
packages are installed the data can also be a 2D NumPy array, a
SciPy sparse array, or a PyGraphviz graph.
multigraph_input : bool or None (default None)
Note: Only used when `incoming_graph_data` is a dict.
If True, `incoming_graph_data` is assumed to be a
dict-of-dict-of-dict-of-dict structure keyed by
node to neighbor to edge keys to edge data for multi-edges.
A NetworkXError is raised if this is not the case.
If False, :func:`to_networkx_graph` is used to try to determine
the dict's graph data structure as either a dict-of-dict-of-dict
keyed by node to neighbor to edge data, or a dict-of-iterable
keyed by node to neighbors.
If None, the treatment for True is tried, but if it fails,
the treatment for False is tried.
attr : keyword arguments, optional (default= no attributes)
Attributes to add to graph as key=value pairs.
See Also
--------
convert
Examples
--------
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G = nx.Graph(name="my graph")
>>> e = [(1, 2), (2, 3), (3, 4)] # list of edges
>>> G = nx.Graph(e)
Arbitrary graph attribute pairs (key=value) may be assigned
>>> G = nx.Graph(e, day="Friday")
>>> G.graph
{'day': 'Friday'}
"""
# multigraph_input can be None/True/False. So check "is not False"
if isinstance(incoming_graph_data, dict) and multigraph_input is not False:
DiGraph.__init__(self)
try:
convert.from_dict_of_dicts(
incoming_graph_data, create_using=self, multigraph_input=True
)
self.graph.update(attr)
except Exception as err:
if multigraph_input is True:
raise nx.NetworkXError(
f"converting multigraph_input raised:\n{type(err)}: {err}"
)
DiGraph.__init__(self, incoming_graph_data, **attr)
else:
DiGraph.__init__(self, incoming_graph_data, **attr)
| (self, incoming_graph_data=None, multigraph_input=None, **attr) |
30,183 | networkx.classes.multidigraph | add_edge | Add an edge between u and v.
The nodes u and v will be automatically added if they are
not already in the graph.
Edge attributes can be specified with keywords or by directly
accessing the edge's attribute dictionary. See examples below.
Parameters
----------
u_for_edge, v_for_edge : nodes
Nodes can be, for example, strings or numbers.
Nodes must be hashable (and not None) Python objects.
key : hashable identifier, optional (default=lowest unused integer)
Used to distinguish multiedges between a pair of nodes.
attr : keyword arguments, optional
Edge data (or labels or objects) can be assigned using
keyword arguments.
Returns
-------
The edge key assigned to the edge.
See Also
--------
add_edges_from : add a collection of edges
Notes
-----
To replace/update edge data, use the optional key argument
to identify a unique edge. Otherwise a new edge will be created.
NetworkX algorithms designed for weighted graphs cannot use
multigraphs directly because it is not clear how to handle
multiedge weights. Convert to Graph using edge attribute
'weight' to enable weighted graph algorithms.
Default keys are generated using the method `new_edge_key()`.
This method can be overridden by subclassing the base class and
providing a custom `new_edge_key()` method.
Examples
--------
The following all add the edge e=(1, 2) to graph G:
>>> G = nx.MultiDiGraph()
>>> e = (1, 2)
>>> key = G.add_edge(1, 2) # explicit two-node form
>>> G.add_edge(*e) # single edge as tuple of two nodes
1
>>> G.add_edges_from([(1, 2)]) # add edges from iterable container
[2]
Associate data to edges using keywords:
>>> key = G.add_edge(1, 2, weight=3)
>>> key = G.add_edge(1, 2, key=0, weight=4) # update data for key=0
>>> key = G.add_edge(1, 3, weight=7, capacity=15, length=342.7)
For non-string attribute keys, use subscript notation.
>>> ekey = G.add_edge(1, 2)
>>> G[1][2][0].update({0: 5})
>>> G.edges[1, 2, 0].update({0: 5})
| def add_edge(self, u_for_edge, v_for_edge, key=None, **attr):
"""Add an edge between u and v.
The nodes u and v will be automatically added if they are
not already in the graph.
Edge attributes can be specified with keywords or by directly
accessing the edge's attribute dictionary. See examples below.
Parameters
----------
u_for_edge, v_for_edge : nodes
Nodes can be, for example, strings or numbers.
Nodes must be hashable (and not None) Python objects.
key : hashable identifier, optional (default=lowest unused integer)
Used to distinguish multiedges between a pair of nodes.
attr : keyword arguments, optional
Edge data (or labels or objects) can be assigned using
keyword arguments.
Returns
-------
The edge key assigned to the edge.
See Also
--------
add_edges_from : add a collection of edges
Notes
-----
To replace/update edge data, use the optional key argument
to identify a unique edge. Otherwise a new edge will be created.
NetworkX algorithms designed for weighted graphs cannot use
multigraphs directly because it is not clear how to handle
multiedge weights. Convert to Graph using edge attribute
'weight' to enable weighted graph algorithms.
Default keys are generated using the method `new_edge_key()`.
This method can be overridden by subclassing the base class and
providing a custom `new_edge_key()` method.
Examples
--------
The following all add the edge e=(1, 2) to graph G:
>>> G = nx.MultiDiGraph()
>>> e = (1, 2)
>>> key = G.add_edge(1, 2) # explicit two-node form
>>> G.add_edge(*e) # single edge as tuple of two nodes
1
>>> G.add_edges_from([(1, 2)]) # add edges from iterable container
[2]
Associate data to edges using keywords:
>>> key = G.add_edge(1, 2, weight=3)
>>> key = G.add_edge(1, 2, key=0, weight=4) # update data for key=0
>>> key = G.add_edge(1, 3, weight=7, capacity=15, length=342.7)
For non-string attribute keys, use subscript notation.
>>> ekey = G.add_edge(1, 2)
>>> G[1][2][0].update({0: 5})
>>> G.edges[1, 2, 0].update({0: 5})
"""
u, v = u_for_edge, v_for_edge
# add nodes
if u not in self._succ:
if u is None:
raise ValueError("None cannot be a node")
self._succ[u] = self.adjlist_inner_dict_factory()
self._pred[u] = self.adjlist_inner_dict_factory()
self._node[u] = self.node_attr_dict_factory()
if v not in self._succ:
if v is None:
raise ValueError("None cannot be a node")
self._succ[v] = self.adjlist_inner_dict_factory()
self._pred[v] = self.adjlist_inner_dict_factory()
self._node[v] = self.node_attr_dict_factory()
if key is None:
key = self.new_edge_key(u, v)
if v in self._succ[u]:
keydict = self._adj[u][v]
datadict = keydict.get(key, self.edge_attr_dict_factory())
datadict.update(attr)
keydict[key] = datadict
else:
# selfloops work this way without special treatment
datadict = self.edge_attr_dict_factory()
datadict.update(attr)
keydict = self.edge_key_dict_factory()
keydict[key] = datadict
self._succ[u][v] = keydict
self._pred[v][u] = keydict
nx._clear_cache(self)
return key
| (self, u_for_edge, v_for_edge, key=None, **attr) |
30,184 | networkx.classes.multigraph | add_edges_from | Add all the edges in ebunch_to_add.
Parameters
----------
ebunch_to_add : container of edges
Each edge given in the container will be added to the
graph. The edges can be:
- 2-tuples (u, v) or
- 3-tuples (u, v, d) for an edge data dict d, or
- 3-tuples (u, v, k) for not iterable key k, or
- 4-tuples (u, v, k, d) for an edge with data and key k
attr : keyword arguments, optional
Edge data (or labels or objects) can be assigned using
keyword arguments.
Returns
-------
A list of edge keys assigned to the edges in `ebunch`.
See Also
--------
add_edge : add a single edge
add_weighted_edges_from : convenient way to add weighted edges
Notes
-----
Adding the same edge twice has no effect but any edge data
will be updated when each duplicate edge is added.
Edge attributes specified in an ebunch take precedence over
attributes specified via keyword arguments.
Default keys are generated using the method ``new_edge_key()``.
This method can be overridden by subclassing the base class and
providing a custom ``new_edge_key()`` method.
When adding edges from an iterator over the graph you are changing,
a `RuntimeError` can be raised with message:
`RuntimeError: dictionary changed size during iteration`. This
happens when the graph's underlying dictionary is modified during
iteration. To avoid this error, evaluate the iterator into a separate
object, e.g. by using `list(iterator_of_edges)`, and pass this
object to `G.add_edges_from`.
Examples
--------
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.add_edges_from([(0, 1), (1, 2)]) # using a list of edge tuples
>>> e = zip(range(0, 3), range(1, 4))
>>> G.add_edges_from(e) # Add the path graph 0-1-2-3
Associate data to edges
>>> G.add_edges_from([(1, 2), (2, 3)], weight=3)
>>> G.add_edges_from([(3, 4), (1, 4)], label="WN2898")
Evaluate an iterator over a graph if using it to modify the same graph
>>> G = nx.MultiGraph([(1, 2), (2, 3), (3, 4)])
>>> # Grow graph by one new node, adding edges to all existing nodes.
>>> # wrong way - will raise RuntimeError
>>> # G.add_edges_from(((5, n) for n in G.nodes))
>>> # right way - note that there will be no self-edge for node 5
>>> assigned_keys = G.add_edges_from(list((5, n) for n in G.nodes))
| def add_edges_from(self, ebunch_to_add, **attr):
"""Add all the edges in ebunch_to_add.
Parameters
----------
ebunch_to_add : container of edges
Each edge given in the container will be added to the
graph. The edges can be:
- 2-tuples (u, v) or
- 3-tuples (u, v, d) for an edge data dict d, or
- 3-tuples (u, v, k) for not iterable key k, or
- 4-tuples (u, v, k, d) for an edge with data and key k
attr : keyword arguments, optional
Edge data (or labels or objects) can be assigned using
keyword arguments.
Returns
-------
A list of edge keys assigned to the edges in `ebunch`.
See Also
--------
add_edge : add a single edge
add_weighted_edges_from : convenient way to add weighted edges
Notes
-----
Adding the same edge twice has no effect but any edge data
will be updated when each duplicate edge is added.
Edge attributes specified in an ebunch take precedence over
attributes specified via keyword arguments.
Default keys are generated using the method ``new_edge_key()``.
This method can be overridden by subclassing the base class and
providing a custom ``new_edge_key()`` method.
When adding edges from an iterator over the graph you are changing,
a `RuntimeError` can be raised with message:
`RuntimeError: dictionary changed size during iteration`. This
happens when the graph's underlying dictionary is modified during
iteration. To avoid this error, evaluate the iterator into a separate
object, e.g. by using `list(iterator_of_edges)`, and pass this
object to `G.add_edges_from`.
Examples
--------
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.add_edges_from([(0, 1), (1, 2)]) # using a list of edge tuples
>>> e = zip(range(0, 3), range(1, 4))
>>> G.add_edges_from(e) # Add the path graph 0-1-2-3
Associate data to edges
>>> G.add_edges_from([(1, 2), (2, 3)], weight=3)
>>> G.add_edges_from([(3, 4), (1, 4)], label="WN2898")
Evaluate an iterator over a graph if using it to modify the same graph
>>> G = nx.MultiGraph([(1, 2), (2, 3), (3, 4)])
>>> # Grow graph by one new node, adding edges to all existing nodes.
>>> # wrong way - will raise RuntimeError
>>> # G.add_edges_from(((5, n) for n in G.nodes))
>>> # right way - note that there will be no self-edge for node 5
>>> assigned_keys = G.add_edges_from(list((5, n) for n in G.nodes))
"""
keylist = []
for e in ebunch_to_add:
ne = len(e)
if ne == 4:
u, v, key, dd = e
elif ne == 3:
u, v, dd = e
key = None
elif ne == 2:
u, v = e
dd = {}
key = None
else:
msg = f"Edge tuple {e} must be a 2-tuple, 3-tuple or 4-tuple."
raise NetworkXError(msg)
ddd = {}
ddd.update(attr)
try:
ddd.update(dd)
except (TypeError, ValueError):
if ne != 3:
raise
key = dd # ne == 3 with 3rd value not dict, must be a key
key = self.add_edge(u, v, key)
self[u][v][key].update(ddd)
keylist.append(key)
nx._clear_cache(self)
return keylist
| (self, ebunch_to_add, **attr) |
30,191 | networkx.classes.multigraph | copy | Returns a copy of the graph.
The copy method by default returns an independent shallow copy
of the graph and attributes. That is, if an attribute is a
container, that container is shared by the original an the copy.
Use Python's `copy.deepcopy` for new containers.
If `as_view` is True then a view is returned instead of a copy.
Notes
-----
All copies reproduce the graph structure, but data attributes
may be handled in different ways. There are four types of copies
of a graph that people might want.
Deepcopy -- A "deepcopy" copies the graph structure as well as
all data attributes and any objects they might contain.
The entire graph object is new so that changes in the copy
do not affect the original object. (see Python's copy.deepcopy)
Data Reference (Shallow) -- For a shallow copy the graph structure
is copied but the edge, node and graph attribute dicts are
references to those in the original graph. This saves
time and memory but could cause confusion if you change an attribute
in one graph and it changes the attribute in the other.
NetworkX does not provide this level of shallow copy.
Independent Shallow -- This copy creates new independent attribute
dicts and then does a shallow copy of the attributes. That is, any
attributes that are containers are shared between the new graph
and the original. This is exactly what `dict.copy()` provides.
You can obtain this style copy using:
>>> G = nx.path_graph(5)
>>> H = G.copy()
>>> H = G.copy(as_view=False)
>>> H = nx.Graph(G)
>>> H = G.__class__(G)
Fresh Data -- For fresh data, the graph structure is copied while
new empty data attribute dicts are created. The resulting graph
is independent of the original and it has no edge, node or graph
attributes. Fresh copies are not enabled. Instead use:
>>> H = G.__class__()
>>> H.add_nodes_from(G)
>>> H.add_edges_from(G.edges)
View -- Inspired by dict-views, graph-views act like read-only
versions of the original graph, providing a copy of the original
structure without requiring any memory for copying the information.
See the Python copy module for more information on shallow
and deep copies, https://docs.python.org/3/library/copy.html.
Parameters
----------
as_view : bool, optional (default=False)
If True, the returned graph-view provides a read-only view
of the original graph without actually copying any data.
Returns
-------
G : Graph
A copy of the graph.
See Also
--------
to_directed: return a directed copy of the graph.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> H = G.copy()
| def copy(self, as_view=False):
"""Returns a copy of the graph.
The copy method by default returns an independent shallow copy
of the graph and attributes. That is, if an attribute is a
container, that container is shared by the original an the copy.
Use Python's `copy.deepcopy` for new containers.
If `as_view` is True then a view is returned instead of a copy.
Notes
-----
All copies reproduce the graph structure, but data attributes
may be handled in different ways. There are four types of copies
of a graph that people might want.
Deepcopy -- A "deepcopy" copies the graph structure as well as
all data attributes and any objects they might contain.
The entire graph object is new so that changes in the copy
do not affect the original object. (see Python's copy.deepcopy)
Data Reference (Shallow) -- For a shallow copy the graph structure
is copied but the edge, node and graph attribute dicts are
references to those in the original graph. This saves
time and memory but could cause confusion if you change an attribute
in one graph and it changes the attribute in the other.
NetworkX does not provide this level of shallow copy.
Independent Shallow -- This copy creates new independent attribute
dicts and then does a shallow copy of the attributes. That is, any
attributes that are containers are shared between the new graph
and the original. This is exactly what `dict.copy()` provides.
You can obtain this style copy using:
>>> G = nx.path_graph(5)
>>> H = G.copy()
>>> H = G.copy(as_view=False)
>>> H = nx.Graph(G)
>>> H = G.__class__(G)
Fresh Data -- For fresh data, the graph structure is copied while
new empty data attribute dicts are created. The resulting graph
is independent of the original and it has no edge, node or graph
attributes. Fresh copies are not enabled. Instead use:
>>> H = G.__class__()
>>> H.add_nodes_from(G)
>>> H.add_edges_from(G.edges)
View -- Inspired by dict-views, graph-views act like read-only
versions of the original graph, providing a copy of the original
structure without requiring any memory for copying the information.
See the Python copy module for more information on shallow
and deep copies, https://docs.python.org/3/library/copy.html.
Parameters
----------
as_view : bool, optional (default=False)
If True, the returned graph-view provides a read-only view
of the original graph without actually copying any data.
Returns
-------
G : Graph
A copy of the graph.
See Also
--------
to_directed: return a directed copy of the graph.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> H = G.copy()
"""
if as_view is True:
return nx.graphviews.generic_graph_view(self)
G = self.__class__()
G.graph.update(self.graph)
G.add_nodes_from((n, d.copy()) for n, d in self._node.items())
G.add_edges_from(
(u, v, key, datadict.copy())
for u, nbrs in self._adj.items()
for v, keydict in nbrs.items()
for key, datadict in keydict.items()
)
return G
| (self, as_view=False) |
30,193 | networkx.classes.multigraph | get_edge_data | Returns the attribute dictionary associated with edge (u, v,
key).
If a key is not provided, returns a dictionary mapping edge keys
to attribute dictionaries for each edge between u and v.
This is identical to `G[u][v][key]` except the default is returned
instead of an exception is the edge doesn't exist.
Parameters
----------
u, v : nodes
default : any Python object (default=None)
Value to return if the specific edge (u, v, key) is not
found, OR if there are no edges between u and v and no key
is specified.
key : hashable identifier, optional (default=None)
Return data only for the edge with specified key, as an
attribute dictionary (rather than a dictionary mapping keys
to attribute dictionaries).
Returns
-------
edge_dict : dictionary
The edge attribute dictionary, OR a dictionary mapping edge
keys to attribute dictionaries for each of those edges if no
specific key is provided (even if there's only one edge
between u and v).
Examples
--------
>>> G = nx.MultiGraph() # or MultiDiGraph
>>> key = G.add_edge(0, 1, key="a", weight=7)
>>> G[0][1]["a"] # key='a'
{'weight': 7}
>>> G.edges[0, 1, "a"] # key='a'
{'weight': 7}
Warning: we protect the graph data structure by making
`G.edges` and `G[1][2]` read-only dict-like structures.
However, you can assign values to attributes in e.g.
`G.edges[1, 2, 'a']` or `G[1][2]['a']` using an additional
bracket as shown next. You need to specify all edge info
to assign to the edge data associated with an edge.
>>> G[0][1]["a"]["weight"] = 10
>>> G.edges[0, 1, "a"]["weight"] = 10
>>> G[0][1]["a"]["weight"]
10
>>> G.edges[1, 0, "a"]["weight"]
10
>>> G = nx.MultiGraph() # or MultiDiGraph
>>> nx.add_path(G, [0, 1, 2, 3])
>>> G.edges[0, 1, 0]["weight"] = 5
>>> G.get_edge_data(0, 1)
{0: {'weight': 5}}
>>> e = (0, 1)
>>> G.get_edge_data(*e) # tuple form
{0: {'weight': 5}}
>>> G.get_edge_data(3, 0) # edge not in graph, returns None
>>> G.get_edge_data(3, 0, default=0) # edge not in graph, return default
0
>>> G.get_edge_data(1, 0, 0) # specific key gives back
{'weight': 5}
| def get_edge_data(self, u, v, key=None, default=None):
"""Returns the attribute dictionary associated with edge (u, v,
key).
If a key is not provided, returns a dictionary mapping edge keys
to attribute dictionaries for each edge between u and v.
This is identical to `G[u][v][key]` except the default is returned
instead of an exception is the edge doesn't exist.
Parameters
----------
u, v : nodes
default : any Python object (default=None)
Value to return if the specific edge (u, v, key) is not
found, OR if there are no edges between u and v and no key
is specified.
key : hashable identifier, optional (default=None)
Return data only for the edge with specified key, as an
attribute dictionary (rather than a dictionary mapping keys
to attribute dictionaries).
Returns
-------
edge_dict : dictionary
The edge attribute dictionary, OR a dictionary mapping edge
keys to attribute dictionaries for each of those edges if no
specific key is provided (even if there's only one edge
between u and v).
Examples
--------
>>> G = nx.MultiGraph() # or MultiDiGraph
>>> key = G.add_edge(0, 1, key="a", weight=7)
>>> G[0][1]["a"] # key='a'
{'weight': 7}
>>> G.edges[0, 1, "a"] # key='a'
{'weight': 7}
Warning: we protect the graph data structure by making
`G.edges` and `G[1][2]` read-only dict-like structures.
However, you can assign values to attributes in e.g.
`G.edges[1, 2, 'a']` or `G[1][2]['a']` using an additional
bracket as shown next. You need to specify all edge info
to assign to the edge data associated with an edge.
>>> G[0][1]["a"]["weight"] = 10
>>> G.edges[0, 1, "a"]["weight"] = 10
>>> G[0][1]["a"]["weight"]
10
>>> G.edges[1, 0, "a"]["weight"]
10
>>> G = nx.MultiGraph() # or MultiDiGraph
>>> nx.add_path(G, [0, 1, 2, 3])
>>> G.edges[0, 1, 0]["weight"] = 5
>>> G.get_edge_data(0, 1)
{0: {'weight': 5}}
>>> e = (0, 1)
>>> G.get_edge_data(*e) # tuple form
{0: {'weight': 5}}
>>> G.get_edge_data(3, 0) # edge not in graph, returns None
>>> G.get_edge_data(3, 0, default=0) # edge not in graph, return default
0
>>> G.get_edge_data(1, 0, 0) # specific key gives back
{'weight': 5}
"""
try:
if key is None:
return self._adj[u][v]
else:
return self._adj[u][v][key]
except KeyError:
return default
| (self, u, v, key=None, default=None) |
30,194 | networkx.classes.multigraph | has_edge | Returns True if the graph has an edge between nodes u and v.
This is the same as `v in G[u] or key in G[u][v]`
without KeyError exceptions.
Parameters
----------
u, v : nodes
Nodes can be, for example, strings or numbers.
key : hashable identifier, optional (default=None)
If specified return True only if the edge with
key is found.
Returns
-------
edge_ind : bool
True if edge is in the graph, False otherwise.
Examples
--------
Can be called either using two nodes u, v, an edge tuple (u, v),
or an edge tuple (u, v, key).
>>> G = nx.MultiGraph() # or MultiDiGraph
>>> nx.add_path(G, [0, 1, 2, 3])
>>> G.has_edge(0, 1) # using two nodes
True
>>> e = (0, 1)
>>> G.has_edge(*e) # e is a 2-tuple (u, v)
True
>>> G.add_edge(0, 1, key="a")
'a'
>>> G.has_edge(0, 1, key="a") # specify key
True
>>> G.has_edge(1, 0, key="a") # edges aren't directed
True
>>> e = (0, 1, "a")
>>> G.has_edge(*e) # e is a 3-tuple (u, v, 'a')
True
The following syntax are equivalent:
>>> G.has_edge(0, 1)
True
>>> 1 in G[0] # though this gives :exc:`KeyError` if 0 not in G
True
>>> 0 in G[1] # other order; also gives :exc:`KeyError` if 0 not in G
True
| def has_edge(self, u, v, key=None):
"""Returns True if the graph has an edge between nodes u and v.
This is the same as `v in G[u] or key in G[u][v]`
without KeyError exceptions.
Parameters
----------
u, v : nodes
Nodes can be, for example, strings or numbers.
key : hashable identifier, optional (default=None)
If specified return True only if the edge with
key is found.
Returns
-------
edge_ind : bool
True if edge is in the graph, False otherwise.
Examples
--------
Can be called either using two nodes u, v, an edge tuple (u, v),
or an edge tuple (u, v, key).
>>> G = nx.MultiGraph() # or MultiDiGraph
>>> nx.add_path(G, [0, 1, 2, 3])
>>> G.has_edge(0, 1) # using two nodes
True
>>> e = (0, 1)
>>> G.has_edge(*e) # e is a 2-tuple (u, v)
True
>>> G.add_edge(0, 1, key="a")
'a'
>>> G.has_edge(0, 1, key="a") # specify key
True
>>> G.has_edge(1, 0, key="a") # edges aren't directed
True
>>> e = (0, 1, "a")
>>> G.has_edge(*e) # e is a 3-tuple (u, v, 'a')
True
The following syntax are equivalent:
>>> G.has_edge(0, 1)
True
>>> 1 in G[0] # though this gives :exc:`KeyError` if 0 not in G
True
>>> 0 in G[1] # other order; also gives :exc:`KeyError` if 0 not in G
True
"""
try:
if key is None:
return v in self._adj[u]
else:
return key in self._adj[u][v]
except KeyError:
return False
| (self, u, v, key=None) |
30,199 | networkx.classes.multidigraph | is_multigraph | Returns True if graph is a multigraph, False otherwise. | def is_multigraph(self):
"""Returns True if graph is a multigraph, False otherwise."""
return True
| (self) |
30,202 | networkx.classes.multigraph | new_edge_key | Returns an unused key for edges between nodes `u` and `v`.
The nodes `u` and `v` do not need to be already in the graph.
Notes
-----
In the standard MultiGraph class the new key is the number of existing
edges between `u` and `v` (increased if necessary to ensure unused).
The first edge will have key 0, then 1, etc. If an edge is removed
further new_edge_keys may not be in this order.
Parameters
----------
u, v : nodes
Returns
-------
key : int
| def new_edge_key(self, u, v):
"""Returns an unused key for edges between nodes `u` and `v`.
The nodes `u` and `v` do not need to be already in the graph.
Notes
-----
In the standard MultiGraph class the new key is the number of existing
edges between `u` and `v` (increased if necessary to ensure unused).
The first edge will have key 0, then 1, etc. If an edge is removed
further new_edge_keys may not be in this order.
Parameters
----------
u, v : nodes
Returns
-------
key : int
"""
try:
keydict = self._adj[u][v]
except KeyError:
return 0
key = len(keydict)
while key in keydict:
key += 1
return key
| (self, u, v) |
30,203 | networkx.classes.multigraph | number_of_edges | Returns the number of edges between two nodes.
Parameters
----------
u, v : nodes, optional (Default=all edges)
If u and v are specified, return the number of edges between
u and v. Otherwise return the total number of all edges.
Returns
-------
nedges : int
The number of edges in the graph. If nodes `u` and `v` are
specified return the number of edges between those nodes. If
the graph is directed, this only returns the number of edges
from `u` to `v`.
See Also
--------
size
Examples
--------
For undirected multigraphs, this method counts the total number
of edges in the graph::
>>> G = nx.MultiGraph()
>>> G.add_edges_from([(0, 1), (0, 1), (1, 2)])
[0, 1, 0]
>>> G.number_of_edges()
3
If you specify two nodes, this counts the total number of edges
joining the two nodes::
>>> G.number_of_edges(0, 1)
2
For directed multigraphs, this method can count the total number
of directed edges from `u` to `v`::
>>> G = nx.MultiDiGraph()
>>> G.add_edges_from([(0, 1), (0, 1), (1, 0)])
[0, 1, 0]
>>> G.number_of_edges(0, 1)
2
>>> G.number_of_edges(1, 0)
1
| def number_of_edges(self, u=None, v=None):
"""Returns the number of edges between two nodes.
Parameters
----------
u, v : nodes, optional (Default=all edges)
If u and v are specified, return the number of edges between
u and v. Otherwise return the total number of all edges.
Returns
-------
nedges : int
The number of edges in the graph. If nodes `u` and `v` are
specified return the number of edges between those nodes. If
the graph is directed, this only returns the number of edges
from `u` to `v`.
See Also
--------
size
Examples
--------
For undirected multigraphs, this method counts the total number
of edges in the graph::
>>> G = nx.MultiGraph()
>>> G.add_edges_from([(0, 1), (0, 1), (1, 2)])
[0, 1, 0]
>>> G.number_of_edges()
3
If you specify two nodes, this counts the total number of edges
joining the two nodes::
>>> G.number_of_edges(0, 1)
2
For directed multigraphs, this method can count the total number
of directed edges from `u` to `v`::
>>> G = nx.MultiDiGraph()
>>> G.add_edges_from([(0, 1), (0, 1), (1, 0)])
[0, 1, 0]
>>> G.number_of_edges(0, 1)
2
>>> G.number_of_edges(1, 0)
1
"""
if u is None:
return self.size()
try:
edgedata = self._adj[u][v]
except KeyError:
return 0 # no such edge
return len(edgedata)
| (self, u=None, v=None) |
30,207 | networkx.classes.multidigraph | remove_edge | Remove an edge between u and v.
Parameters
----------
u, v : nodes
Remove an edge between nodes u and v.
key : hashable identifier, optional (default=None)
Used to distinguish multiple edges between a pair of nodes.
If None, remove a single edge between u and v. If there are
multiple edges, removes the last edge added in terms of
insertion order.
Raises
------
NetworkXError
If there is not an edge between u and v, or
if there is no edge with the specified key.
See Also
--------
remove_edges_from : remove a collection of edges
Examples
--------
>>> G = nx.MultiDiGraph()
>>> nx.add_path(G, [0, 1, 2, 3])
>>> G.remove_edge(0, 1)
>>> e = (1, 2)
>>> G.remove_edge(*e) # unpacks e from an edge tuple
For multiple edges
>>> G = nx.MultiDiGraph()
>>> G.add_edges_from([(1, 2), (1, 2), (1, 2)]) # key_list returned
[0, 1, 2]
When ``key=None`` (the default), edges are removed in the opposite
order that they were added:
>>> G.remove_edge(1, 2)
>>> G.edges(keys=True)
OutMultiEdgeView([(1, 2, 0), (1, 2, 1)])
For edges with keys
>>> G = nx.MultiDiGraph()
>>> G.add_edge(1, 2, key="first")
'first'
>>> G.add_edge(1, 2, key="second")
'second'
>>> G.remove_edge(1, 2, key="first")
>>> G.edges(keys=True)
OutMultiEdgeView([(1, 2, 'second')])
| def remove_edge(self, u, v, key=None):
"""Remove an edge between u and v.
Parameters
----------
u, v : nodes
Remove an edge between nodes u and v.
key : hashable identifier, optional (default=None)
Used to distinguish multiple edges between a pair of nodes.
If None, remove a single edge between u and v. If there are
multiple edges, removes the last edge added in terms of
insertion order.
Raises
------
NetworkXError
If there is not an edge between u and v, or
if there is no edge with the specified key.
See Also
--------
remove_edges_from : remove a collection of edges
Examples
--------
>>> G = nx.MultiDiGraph()
>>> nx.add_path(G, [0, 1, 2, 3])
>>> G.remove_edge(0, 1)
>>> e = (1, 2)
>>> G.remove_edge(*e) # unpacks e from an edge tuple
For multiple edges
>>> G = nx.MultiDiGraph()
>>> G.add_edges_from([(1, 2), (1, 2), (1, 2)]) # key_list returned
[0, 1, 2]
When ``key=None`` (the default), edges are removed in the opposite
order that they were added:
>>> G.remove_edge(1, 2)
>>> G.edges(keys=True)
OutMultiEdgeView([(1, 2, 0), (1, 2, 1)])
For edges with keys
>>> G = nx.MultiDiGraph()
>>> G.add_edge(1, 2, key="first")
'first'
>>> G.add_edge(1, 2, key="second")
'second'
>>> G.remove_edge(1, 2, key="first")
>>> G.edges(keys=True)
OutMultiEdgeView([(1, 2, 'second')])
"""
try:
d = self._adj[u][v]
except KeyError as err:
raise NetworkXError(f"The edge {u}-{v} is not in the graph.") from err
# remove the edge with specified data
if key is None:
d.popitem()
else:
try:
del d[key]
except KeyError as err:
msg = f"The edge {u}-{v} with key {key} is not in the graph."
raise NetworkXError(msg) from err
if len(d) == 0:
# remove the key entries if last edge
del self._succ[u][v]
del self._pred[v][u]
nx._clear_cache(self)
| (self, u, v, key=None) |
30,208 | networkx.classes.multigraph | remove_edges_from | Remove all edges specified in ebunch.
Parameters
----------
ebunch: list or container of edge tuples
Each edge given in the list or container will be removed
from the graph. The edges can be:
- 2-tuples (u, v) A single edge between u and v is removed.
- 3-tuples (u, v, key) The edge identified by key is removed.
- 4-tuples (u, v, key, data) where data is ignored.
See Also
--------
remove_edge : remove a single edge
Notes
-----
Will fail silently if an edge in ebunch is not in the graph.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> ebunch = [(1, 2), (2, 3)]
>>> G.remove_edges_from(ebunch)
Removing multiple copies of edges
>>> G = nx.MultiGraph()
>>> keys = G.add_edges_from([(1, 2), (1, 2), (1, 2)])
>>> G.remove_edges_from([(1, 2), (2, 1)]) # edges aren't directed
>>> list(G.edges())
[(1, 2)]
>>> G.remove_edges_from([(1, 2), (1, 2)]) # silently ignore extra copy
>>> list(G.edges) # now empty graph
[]
When the edge is a 2-tuple ``(u, v)`` but there are multiple edges between
u and v in the graph, the most recent edge (in terms of insertion
order) is removed.
>>> G = nx.MultiGraph()
>>> for key in ("x", "y", "a"):
... k = G.add_edge(0, 1, key=key)
>>> G.edges(keys=True)
MultiEdgeView([(0, 1, 'x'), (0, 1, 'y'), (0, 1, 'a')])
>>> G.remove_edges_from([(0, 1)])
>>> G.edges(keys=True)
MultiEdgeView([(0, 1, 'x'), (0, 1, 'y')])
| def remove_edges_from(self, ebunch):
"""Remove all edges specified in ebunch.
Parameters
----------
ebunch: list or container of edge tuples
Each edge given in the list or container will be removed
from the graph. The edges can be:
- 2-tuples (u, v) A single edge between u and v is removed.
- 3-tuples (u, v, key) The edge identified by key is removed.
- 4-tuples (u, v, key, data) where data is ignored.
See Also
--------
remove_edge : remove a single edge
Notes
-----
Will fail silently if an edge in ebunch is not in the graph.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> ebunch = [(1, 2), (2, 3)]
>>> G.remove_edges_from(ebunch)
Removing multiple copies of edges
>>> G = nx.MultiGraph()
>>> keys = G.add_edges_from([(1, 2), (1, 2), (1, 2)])
>>> G.remove_edges_from([(1, 2), (2, 1)]) # edges aren't directed
>>> list(G.edges())
[(1, 2)]
>>> G.remove_edges_from([(1, 2), (1, 2)]) # silently ignore extra copy
>>> list(G.edges) # now empty graph
[]
When the edge is a 2-tuple ``(u, v)`` but there are multiple edges between
u and v in the graph, the most recent edge (in terms of insertion
order) is removed.
>>> G = nx.MultiGraph()
>>> for key in ("x", "y", "a"):
... k = G.add_edge(0, 1, key=key)
>>> G.edges(keys=True)
MultiEdgeView([(0, 1, 'x'), (0, 1, 'y'), (0, 1, 'a')])
>>> G.remove_edges_from([(0, 1)])
>>> G.edges(keys=True)
MultiEdgeView([(0, 1, 'x'), (0, 1, 'y')])
"""
for e in ebunch:
try:
self.remove_edge(*e[:3])
except NetworkXError:
pass
nx._clear_cache(self)
| (self, ebunch) |
30,211 | networkx.classes.multidigraph | reverse | Returns the reverse of the graph.
The reverse is a graph with the same nodes and edges
but with the directions of the edges reversed.
Parameters
----------
copy : bool optional (default=True)
If True, return a new DiGraph holding the reversed edges.
If False, the reverse graph is created using a view of
the original graph.
| def reverse(self, copy=True):
"""Returns the reverse of the graph.
The reverse is a graph with the same nodes and edges
but with the directions of the edges reversed.
Parameters
----------
copy : bool optional (default=True)
If True, return a new DiGraph holding the reversed edges.
If False, the reverse graph is created using a view of
the original graph.
"""
if copy:
H = self.__class__()
H.graph.update(deepcopy(self.graph))
H.add_nodes_from((n, deepcopy(d)) for n, d in self._node.items())
H.add_edges_from(
(v, u, k, deepcopy(d))
for u, v, k, d in self.edges(keys=True, data=True)
)
return H
return nx.reverse_view(self)
| (self, copy=True) |
30,215 | networkx.classes.multigraph | to_directed | Returns a directed representation of the graph.
Returns
-------
G : MultiDiGraph
A directed graph with the same name, same nodes, and with
each edge (u, v, k, data) replaced by two directed edges
(u, v, k, data) and (v, u, k, data).
Notes
-----
This returns a "deepcopy" of the edge, node, and
graph attributes which attempts to completely copy
all of the data and references.
This is in contrast to the similar D=MultiDiGraph(G) which
returns a shallow copy of the data.
See the Python copy module for more information on shallow
and deep copies, https://docs.python.org/3/library/copy.html.
Warning: If you have subclassed MultiGraph to use dict-like objects
in the data structure, those changes do not transfer to the
MultiDiGraph created by this method.
Examples
--------
>>> G = nx.MultiGraph()
>>> G.add_edge(0, 1)
0
>>> G.add_edge(0, 1)
1
>>> H = G.to_directed()
>>> list(H.edges)
[(0, 1, 0), (0, 1, 1), (1, 0, 0), (1, 0, 1)]
If already directed, return a (deep) copy
>>> G = nx.MultiDiGraph()
>>> G.add_edge(0, 1)
0
>>> H = G.to_directed()
>>> list(H.edges)
[(0, 1, 0)]
| def to_directed(self, as_view=False):
"""Returns a directed representation of the graph.
Returns
-------
G : MultiDiGraph
A directed graph with the same name, same nodes, and with
each edge (u, v, k, data) replaced by two directed edges
(u, v, k, data) and (v, u, k, data).
Notes
-----
This returns a "deepcopy" of the edge, node, and
graph attributes which attempts to completely copy
all of the data and references.
This is in contrast to the similar D=MultiDiGraph(G) which
returns a shallow copy of the data.
See the Python copy module for more information on shallow
and deep copies, https://docs.python.org/3/library/copy.html.
Warning: If you have subclassed MultiGraph to use dict-like objects
in the data structure, those changes do not transfer to the
MultiDiGraph created by this method.
Examples
--------
>>> G = nx.MultiGraph()
>>> G.add_edge(0, 1)
0
>>> G.add_edge(0, 1)
1
>>> H = G.to_directed()
>>> list(H.edges)
[(0, 1, 0), (0, 1, 1), (1, 0, 0), (1, 0, 1)]
If already directed, return a (deep) copy
>>> G = nx.MultiDiGraph()
>>> G.add_edge(0, 1)
0
>>> H = G.to_directed()
>>> list(H.edges)
[(0, 1, 0)]
"""
graph_class = self.to_directed_class()
if as_view is True:
return nx.graphviews.generic_graph_view(self, graph_class)
# deepcopy when not a view
G = graph_class()
G.graph.update(deepcopy(self.graph))
G.add_nodes_from((n, deepcopy(d)) for n, d in self._node.items())
G.add_edges_from(
(u, v, key, deepcopy(datadict))
for u, nbrs in self.adj.items()
for v, keydict in nbrs.items()
for key, datadict in keydict.items()
)
return G
| (self, as_view=False) |
30,216 | networkx.classes.multigraph | to_directed_class | Returns the class to use for empty directed copies.
If you subclass the base classes, use this to designate
what directed class to use for `to_directed()` copies.
| def to_directed_class(self):
"""Returns the class to use for empty directed copies.
If you subclass the base classes, use this to designate
what directed class to use for `to_directed()` copies.
"""
return nx.MultiDiGraph
| (self) |
30,217 | networkx.classes.multidigraph | to_undirected | Returns an undirected representation of the digraph.
Parameters
----------
reciprocal : bool (optional)
If True only keep edges that appear in both directions
in the original digraph.
as_view : bool (optional, default=False)
If True return an undirected view of the original directed graph.
Returns
-------
G : MultiGraph
An undirected graph with the same name and nodes and
with edge (u, v, data) if either (u, v, data) or (v, u, data)
is in the digraph. If both edges exist in digraph and
their edge data is different, only one edge is created
with an arbitrary choice of which edge data to use.
You must check and correct for this manually if desired.
See Also
--------
MultiGraph, copy, add_edge, add_edges_from
Notes
-----
This returns a "deepcopy" of the edge, node, and
graph attributes which attempts to completely copy
all of the data and references.
This is in contrast to the similar D=MultiDiGraph(G) which
returns a shallow copy of the data.
See the Python copy module for more information on shallow
and deep copies, https://docs.python.org/3/library/copy.html.
Warning: If you have subclassed MultiDiGraph to use dict-like
objects in the data structure, those changes do not transfer
to the MultiGraph created by this method.
Examples
--------
>>> G = nx.path_graph(2) # or MultiGraph, etc
>>> H = G.to_directed()
>>> list(H.edges)
[(0, 1), (1, 0)]
>>> G2 = H.to_undirected()
>>> list(G2.edges)
[(0, 1)]
| def to_undirected(self, reciprocal=False, as_view=False):
"""Returns an undirected representation of the digraph.
Parameters
----------
reciprocal : bool (optional)
If True only keep edges that appear in both directions
in the original digraph.
as_view : bool (optional, default=False)
If True return an undirected view of the original directed graph.
Returns
-------
G : MultiGraph
An undirected graph with the same name and nodes and
with edge (u, v, data) if either (u, v, data) or (v, u, data)
is in the digraph. If both edges exist in digraph and
their edge data is different, only one edge is created
with an arbitrary choice of which edge data to use.
You must check and correct for this manually if desired.
See Also
--------
MultiGraph, copy, add_edge, add_edges_from
Notes
-----
This returns a "deepcopy" of the edge, node, and
graph attributes which attempts to completely copy
all of the data and references.
This is in contrast to the similar D=MultiDiGraph(G) which
returns a shallow copy of the data.
See the Python copy module for more information on shallow
and deep copies, https://docs.python.org/3/library/copy.html.
Warning: If you have subclassed MultiDiGraph to use dict-like
objects in the data structure, those changes do not transfer
to the MultiGraph created by this method.
Examples
--------
>>> G = nx.path_graph(2) # or MultiGraph, etc
>>> H = G.to_directed()
>>> list(H.edges)
[(0, 1), (1, 0)]
>>> G2 = H.to_undirected()
>>> list(G2.edges)
[(0, 1)]
"""
graph_class = self.to_undirected_class()
if as_view is True:
return nx.graphviews.generic_graph_view(self, graph_class)
# deepcopy when not a view
G = graph_class()
G.graph.update(deepcopy(self.graph))
G.add_nodes_from((n, deepcopy(d)) for n, d in self._node.items())
if reciprocal is True:
G.add_edges_from(
(u, v, key, deepcopy(data))
for u, nbrs in self._adj.items()
for v, keydict in nbrs.items()
for key, data in keydict.items()
if v in self._pred[u] and key in self._pred[u][v]
)
else:
G.add_edges_from(
(u, v, key, deepcopy(data))
for u, nbrs in self._adj.items()
for v, keydict in nbrs.items()
for key, data in keydict.items()
)
return G
| (self, reciprocal=False, as_view=False) |
30,218 | networkx.classes.multigraph | to_undirected_class | Returns the class to use for empty undirected copies.
If you subclass the base classes, use this to designate
what directed class to use for `to_directed()` copies.
| def to_undirected_class(self):
"""Returns the class to use for empty undirected copies.
If you subclass the base classes, use this to designate
what directed class to use for `to_directed()` copies.
"""
return MultiGraph
| (self) |
30,220 | networkx.classes.multigraph | MultiGraph |
An undirected graph class that can store multiedges.
Multiedges are multiple edges between two nodes. Each edge
can hold optional data or attributes.
A MultiGraph holds undirected edges. Self loops are allowed.
Nodes can be arbitrary (hashable) Python objects with optional
key/value attributes. By convention `None` is not used as a node.
Edges are represented as links between nodes with optional
key/value attributes, in a MultiGraph each edge has a key to
distinguish between multiple edges that have the same source and
destination nodes.
Parameters
----------
incoming_graph_data : input graph (optional, default: None)
Data to initialize graph. If None (default) an empty
graph is created. The data can be any format that is supported
by the to_networkx_graph() function, currently including edge list,
dict of dicts, dict of lists, NetworkX graph, 2D NumPy array,
SciPy sparse array, or PyGraphviz graph.
multigraph_input : bool or None (default None)
Note: Only used when `incoming_graph_data` is a dict.
If True, `incoming_graph_data` is assumed to be a
dict-of-dict-of-dict-of-dict structure keyed by
node to neighbor to edge keys to edge data for multi-edges.
A NetworkXError is raised if this is not the case.
If False, :func:`to_networkx_graph` is used to try to determine
the dict's graph data structure as either a dict-of-dict-of-dict
keyed by node to neighbor to edge data, or a dict-of-iterable
keyed by node to neighbors.
If None, the treatment for True is tried, but if it fails,
the treatment for False is tried.
attr : keyword arguments, optional (default= no attributes)
Attributes to add to graph as key=value pairs.
See Also
--------
Graph
DiGraph
MultiDiGraph
Examples
--------
Create an empty graph structure (a "null graph") with no nodes and
no edges.
>>> G = nx.MultiGraph()
G can be grown in several ways.
**Nodes:**
Add one node at a time:
>>> G.add_node(1)
Add the nodes from any container (a list, dict, set or
even the lines from a file or the nodes from another graph).
>>> G.add_nodes_from([2, 3])
>>> G.add_nodes_from(range(100, 110))
>>> H = nx.path_graph(10)
>>> G.add_nodes_from(H)
In addition to strings and integers any hashable Python object
(except None) can represent a node, e.g. a customized node object,
or even another Graph.
>>> G.add_node(H)
**Edges:**
G can also be grown by adding edges.
Add one edge,
>>> key = G.add_edge(1, 2)
a list of edges,
>>> keys = G.add_edges_from([(1, 2), (1, 3)])
or a collection of edges,
>>> keys = G.add_edges_from(H.edges)
If some edges connect nodes not yet in the graph, the nodes
are added automatically. If an edge already exists, an additional
edge is created and stored using a key to identify the edge.
By default the key is the lowest unused integer.
>>> keys = G.add_edges_from([(4, 5, {"route": 28}), (4, 5, {"route": 37})])
>>> G[4]
AdjacencyView({3: {0: {}}, 5: {0: {}, 1: {'route': 28}, 2: {'route': 37}}})
**Attributes:**
Each graph, node, and edge can hold key/value attribute pairs
in an associated attribute dictionary (the keys must be hashable).
By default these are empty, but can be added or changed using
add_edge, add_node or direct manipulation of the attribute
dictionaries named graph, node and edge respectively.
>>> G = nx.MultiGraph(day="Friday")
>>> G.graph
{'day': 'Friday'}
Add node attributes using add_node(), add_nodes_from() or G.nodes
>>> G.add_node(1, time="5pm")
>>> G.add_nodes_from([3], time="2pm")
>>> G.nodes[1]
{'time': '5pm'}
>>> G.nodes[1]["room"] = 714
>>> del G.nodes[1]["room"] # remove attribute
>>> list(G.nodes(data=True))
[(1, {'time': '5pm'}), (3, {'time': '2pm'})]
Add edge attributes using add_edge(), add_edges_from(), subscript
notation, or G.edges.
>>> key = G.add_edge(1, 2, weight=4.7)
>>> keys = G.add_edges_from([(3, 4), (4, 5)], color="red")
>>> keys = G.add_edges_from([(1, 2, {"color": "blue"}), (2, 3, {"weight": 8})])
>>> G[1][2][0]["weight"] = 4.7
>>> G.edges[1, 2, 0]["weight"] = 4
Warning: we protect the graph data structure by making `G.edges[1,
2, 0]` a read-only dict-like structure. However, you can assign to
attributes in e.g. `G.edges[1, 2, 0]`. Thus, use 2 sets of brackets
to add/change data attributes: `G.edges[1, 2, 0]['weight'] = 4`.
**Shortcuts:**
Many common graph features allow python syntax to speed reporting.
>>> 1 in G # check if node in graph
True
>>> [n for n in G if n < 3] # iterate through nodes
[1, 2]
>>> len(G) # number of nodes in graph
5
>>> G[1] # adjacency dict-like view mapping neighbor -> edge key -> edge attributes
AdjacencyView({2: {0: {'weight': 4}, 1: {'color': 'blue'}}})
Often the best way to traverse all edges of a graph is via the neighbors.
The neighbors are reported as an adjacency-dict `G.adj` or `G.adjacency()`.
>>> for n, nbrsdict in G.adjacency():
... for nbr, keydict in nbrsdict.items():
... for key, eattr in keydict.items():
... if "weight" in eattr:
... # Do something useful with the edges
... pass
But the edges() method is often more convenient:
>>> for u, v, keys, weight in G.edges(data="weight", keys=True):
... if weight is not None:
... # Do something useful with the edges
... pass
**Reporting:**
Simple graph information is obtained using methods and object-attributes.
Reporting usually provides views instead of containers to reduce memory
usage. The views update as the graph is updated similarly to dict-views.
The objects `nodes`, `edges` and `adj` provide access to data attributes
via lookup (e.g. `nodes[n]`, `edges[u, v, k]`, `adj[u][v]`) and iteration
(e.g. `nodes.items()`, `nodes.data('color')`,
`nodes.data('color', default='blue')` and similarly for `edges`)
Views exist for `nodes`, `edges`, `neighbors()`/`adj` and `degree`.
For details on these and other miscellaneous methods, see below.
**Subclasses (Advanced):**
The MultiGraph class uses a dict-of-dict-of-dict-of-dict data structure.
The outer dict (node_dict) holds adjacency information keyed by node.
The next dict (adjlist_dict) represents the adjacency information
and holds edge_key dicts keyed by neighbor. The edge_key dict holds
each edge_attr dict keyed by edge key. The inner dict
(edge_attr_dict) represents the edge data and holds edge attribute
values keyed by attribute names.
Each of these four dicts in the dict-of-dict-of-dict-of-dict
structure can be replaced by a user defined dict-like object.
In general, the dict-like features should be maintained but
extra features can be added. To replace one of the dicts create
a new graph class by changing the class(!) variable holding the
factory for that dict-like structure. The variable names are
node_dict_factory, node_attr_dict_factory, adjlist_inner_dict_factory,
adjlist_outer_dict_factory, edge_key_dict_factory, edge_attr_dict_factory
and graph_attr_dict_factory.
node_dict_factory : function, (default: dict)
Factory function to be used to create the dict containing node
attributes, keyed by node id.
It should require no arguments and return a dict-like object
node_attr_dict_factory: function, (default: dict)
Factory function to be used to create the node attribute
dict which holds attribute values keyed by attribute name.
It should require no arguments and return a dict-like object
adjlist_outer_dict_factory : function, (default: dict)
Factory function to be used to create the outer-most dict
in the data structure that holds adjacency info keyed by node.
It should require no arguments and return a dict-like object.
adjlist_inner_dict_factory : function, (default: dict)
Factory function to be used to create the adjacency list
dict which holds multiedge key dicts keyed by neighbor.
It should require no arguments and return a dict-like object.
edge_key_dict_factory : function, (default: dict)
Factory function to be used to create the edge key dict
which holds edge data keyed by edge key.
It should require no arguments and return a dict-like object.
edge_attr_dict_factory : function, (default: dict)
Factory function to be used to create the edge attribute
dict which holds attribute values keyed by attribute name.
It should require no arguments and return a dict-like object.
graph_attr_dict_factory : function, (default: dict)
Factory function to be used to create the graph attribute
dict which holds attribute values keyed by attribute name.
It should require no arguments and return a dict-like object.
Typically, if your extension doesn't impact the data structure all
methods will inherited without issue except: `to_directed/to_undirected`.
By default these methods create a DiGraph/Graph class and you probably
want them to create your extension of a DiGraph/Graph. To facilitate
this we define two class variables that you can set in your subclass.
to_directed_class : callable, (default: DiGraph or MultiDiGraph)
Class to create a new graph structure in the `to_directed` method.
If `None`, a NetworkX class (DiGraph or MultiDiGraph) is used.
to_undirected_class : callable, (default: Graph or MultiGraph)
Class to create a new graph structure in the `to_undirected` method.
If `None`, a NetworkX class (Graph or MultiGraph) is used.
**Subclassing Example**
Create a low memory graph class that effectively disallows edge
attributes by using a single attribute dict for all edges.
This reduces the memory used, but you lose edge attributes.
>>> class ThinGraph(nx.Graph):
... all_edge_dict = {"weight": 1}
...
... def single_edge_dict(self):
... return self.all_edge_dict
...
... edge_attr_dict_factory = single_edge_dict
>>> G = ThinGraph()
>>> G.add_edge(2, 1)
>>> G[2][1]
{'weight': 1}
>>> G.add_edge(2, 2)
>>> G[2][1] is G[2][2]
True
| class MultiGraph(Graph):
"""
An undirected graph class that can store multiedges.
Multiedges are multiple edges between two nodes. Each edge
can hold optional data or attributes.
A MultiGraph holds undirected edges. Self loops are allowed.
Nodes can be arbitrary (hashable) Python objects with optional
key/value attributes. By convention `None` is not used as a node.
Edges are represented as links between nodes with optional
key/value attributes, in a MultiGraph each edge has a key to
distinguish between multiple edges that have the same source and
destination nodes.
Parameters
----------
incoming_graph_data : input graph (optional, default: None)
Data to initialize graph. If None (default) an empty
graph is created. The data can be any format that is supported
by the to_networkx_graph() function, currently including edge list,
dict of dicts, dict of lists, NetworkX graph, 2D NumPy array,
SciPy sparse array, or PyGraphviz graph.
multigraph_input : bool or None (default None)
Note: Only used when `incoming_graph_data` is a dict.
If True, `incoming_graph_data` is assumed to be a
dict-of-dict-of-dict-of-dict structure keyed by
node to neighbor to edge keys to edge data for multi-edges.
A NetworkXError is raised if this is not the case.
If False, :func:`to_networkx_graph` is used to try to determine
the dict's graph data structure as either a dict-of-dict-of-dict
keyed by node to neighbor to edge data, or a dict-of-iterable
keyed by node to neighbors.
If None, the treatment for True is tried, but if it fails,
the treatment for False is tried.
attr : keyword arguments, optional (default= no attributes)
Attributes to add to graph as key=value pairs.
See Also
--------
Graph
DiGraph
MultiDiGraph
Examples
--------
Create an empty graph structure (a "null graph") with no nodes and
no edges.
>>> G = nx.MultiGraph()
G can be grown in several ways.
**Nodes:**
Add one node at a time:
>>> G.add_node(1)
Add the nodes from any container (a list, dict, set or
even the lines from a file or the nodes from another graph).
>>> G.add_nodes_from([2, 3])
>>> G.add_nodes_from(range(100, 110))
>>> H = nx.path_graph(10)
>>> G.add_nodes_from(H)
In addition to strings and integers any hashable Python object
(except None) can represent a node, e.g. a customized node object,
or even another Graph.
>>> G.add_node(H)
**Edges:**
G can also be grown by adding edges.
Add one edge,
>>> key = G.add_edge(1, 2)
a list of edges,
>>> keys = G.add_edges_from([(1, 2), (1, 3)])
or a collection of edges,
>>> keys = G.add_edges_from(H.edges)
If some edges connect nodes not yet in the graph, the nodes
are added automatically. If an edge already exists, an additional
edge is created and stored using a key to identify the edge.
By default the key is the lowest unused integer.
>>> keys = G.add_edges_from([(4, 5, {"route": 28}), (4, 5, {"route": 37})])
>>> G[4]
AdjacencyView({3: {0: {}}, 5: {0: {}, 1: {'route': 28}, 2: {'route': 37}}})
**Attributes:**
Each graph, node, and edge can hold key/value attribute pairs
in an associated attribute dictionary (the keys must be hashable).
By default these are empty, but can be added or changed using
add_edge, add_node or direct manipulation of the attribute
dictionaries named graph, node and edge respectively.
>>> G = nx.MultiGraph(day="Friday")
>>> G.graph
{'day': 'Friday'}
Add node attributes using add_node(), add_nodes_from() or G.nodes
>>> G.add_node(1, time="5pm")
>>> G.add_nodes_from([3], time="2pm")
>>> G.nodes[1]
{'time': '5pm'}
>>> G.nodes[1]["room"] = 714
>>> del G.nodes[1]["room"] # remove attribute
>>> list(G.nodes(data=True))
[(1, {'time': '5pm'}), (3, {'time': '2pm'})]
Add edge attributes using add_edge(), add_edges_from(), subscript
notation, or G.edges.
>>> key = G.add_edge(1, 2, weight=4.7)
>>> keys = G.add_edges_from([(3, 4), (4, 5)], color="red")
>>> keys = G.add_edges_from([(1, 2, {"color": "blue"}), (2, 3, {"weight": 8})])
>>> G[1][2][0]["weight"] = 4.7
>>> G.edges[1, 2, 0]["weight"] = 4
Warning: we protect the graph data structure by making `G.edges[1,
2, 0]` a read-only dict-like structure. However, you can assign to
attributes in e.g. `G.edges[1, 2, 0]`. Thus, use 2 sets of brackets
to add/change data attributes: `G.edges[1, 2, 0]['weight'] = 4`.
**Shortcuts:**
Many common graph features allow python syntax to speed reporting.
>>> 1 in G # check if node in graph
True
>>> [n for n in G if n < 3] # iterate through nodes
[1, 2]
>>> len(G) # number of nodes in graph
5
>>> G[1] # adjacency dict-like view mapping neighbor -> edge key -> edge attributes
AdjacencyView({2: {0: {'weight': 4}, 1: {'color': 'blue'}}})
Often the best way to traverse all edges of a graph is via the neighbors.
The neighbors are reported as an adjacency-dict `G.adj` or `G.adjacency()`.
>>> for n, nbrsdict in G.adjacency():
... for nbr, keydict in nbrsdict.items():
... for key, eattr in keydict.items():
... if "weight" in eattr:
... # Do something useful with the edges
... pass
But the edges() method is often more convenient:
>>> for u, v, keys, weight in G.edges(data="weight", keys=True):
... if weight is not None:
... # Do something useful with the edges
... pass
**Reporting:**
Simple graph information is obtained using methods and object-attributes.
Reporting usually provides views instead of containers to reduce memory
usage. The views update as the graph is updated similarly to dict-views.
The objects `nodes`, `edges` and `adj` provide access to data attributes
via lookup (e.g. `nodes[n]`, `edges[u, v, k]`, `adj[u][v]`) and iteration
(e.g. `nodes.items()`, `nodes.data('color')`,
`nodes.data('color', default='blue')` and similarly for `edges`)
Views exist for `nodes`, `edges`, `neighbors()`/`adj` and `degree`.
For details on these and other miscellaneous methods, see below.
**Subclasses (Advanced):**
The MultiGraph class uses a dict-of-dict-of-dict-of-dict data structure.
The outer dict (node_dict) holds adjacency information keyed by node.
The next dict (adjlist_dict) represents the adjacency information
and holds edge_key dicts keyed by neighbor. The edge_key dict holds
each edge_attr dict keyed by edge key. The inner dict
(edge_attr_dict) represents the edge data and holds edge attribute
values keyed by attribute names.
Each of these four dicts in the dict-of-dict-of-dict-of-dict
structure can be replaced by a user defined dict-like object.
In general, the dict-like features should be maintained but
extra features can be added. To replace one of the dicts create
a new graph class by changing the class(!) variable holding the
factory for that dict-like structure. The variable names are
node_dict_factory, node_attr_dict_factory, adjlist_inner_dict_factory,
adjlist_outer_dict_factory, edge_key_dict_factory, edge_attr_dict_factory
and graph_attr_dict_factory.
node_dict_factory : function, (default: dict)
Factory function to be used to create the dict containing node
attributes, keyed by node id.
It should require no arguments and return a dict-like object
node_attr_dict_factory: function, (default: dict)
Factory function to be used to create the node attribute
dict which holds attribute values keyed by attribute name.
It should require no arguments and return a dict-like object
adjlist_outer_dict_factory : function, (default: dict)
Factory function to be used to create the outer-most dict
in the data structure that holds adjacency info keyed by node.
It should require no arguments and return a dict-like object.
adjlist_inner_dict_factory : function, (default: dict)
Factory function to be used to create the adjacency list
dict which holds multiedge key dicts keyed by neighbor.
It should require no arguments and return a dict-like object.
edge_key_dict_factory : function, (default: dict)
Factory function to be used to create the edge key dict
which holds edge data keyed by edge key.
It should require no arguments and return a dict-like object.
edge_attr_dict_factory : function, (default: dict)
Factory function to be used to create the edge attribute
dict which holds attribute values keyed by attribute name.
It should require no arguments and return a dict-like object.
graph_attr_dict_factory : function, (default: dict)
Factory function to be used to create the graph attribute
dict which holds attribute values keyed by attribute name.
It should require no arguments and return a dict-like object.
Typically, if your extension doesn't impact the data structure all
methods will inherited without issue except: `to_directed/to_undirected`.
By default these methods create a DiGraph/Graph class and you probably
want them to create your extension of a DiGraph/Graph. To facilitate
this we define two class variables that you can set in your subclass.
to_directed_class : callable, (default: DiGraph or MultiDiGraph)
Class to create a new graph structure in the `to_directed` method.
If `None`, a NetworkX class (DiGraph or MultiDiGraph) is used.
to_undirected_class : callable, (default: Graph or MultiGraph)
Class to create a new graph structure in the `to_undirected` method.
If `None`, a NetworkX class (Graph or MultiGraph) is used.
**Subclassing Example**
Create a low memory graph class that effectively disallows edge
attributes by using a single attribute dict for all edges.
This reduces the memory used, but you lose edge attributes.
>>> class ThinGraph(nx.Graph):
... all_edge_dict = {"weight": 1}
...
... def single_edge_dict(self):
... return self.all_edge_dict
...
... edge_attr_dict_factory = single_edge_dict
>>> G = ThinGraph()
>>> G.add_edge(2, 1)
>>> G[2][1]
{'weight': 1}
>>> G.add_edge(2, 2)
>>> G[2][1] is G[2][2]
True
"""
# node_dict_factory = dict # already assigned in Graph
# adjlist_outer_dict_factory = dict
# adjlist_inner_dict_factory = dict
edge_key_dict_factory = dict
# edge_attr_dict_factory = dict
def to_directed_class(self):
"""Returns the class to use for empty directed copies.
If you subclass the base classes, use this to designate
what directed class to use for `to_directed()` copies.
"""
return nx.MultiDiGraph
def to_undirected_class(self):
"""Returns the class to use for empty undirected copies.
If you subclass the base classes, use this to designate
what directed class to use for `to_directed()` copies.
"""
return MultiGraph
def __init__(self, incoming_graph_data=None, multigraph_input=None, **attr):
"""Initialize a graph with edges, name, or graph attributes.
Parameters
----------
incoming_graph_data : input graph
Data to initialize graph. If incoming_graph_data=None (default)
an empty graph is created. The data can be an edge list, or any
NetworkX graph object. If the corresponding optional Python
packages are installed the data can also be a 2D NumPy array, a
SciPy sparse array, or a PyGraphviz graph.
multigraph_input : bool or None (default None)
Note: Only used when `incoming_graph_data` is a dict.
If True, `incoming_graph_data` is assumed to be a
dict-of-dict-of-dict-of-dict structure keyed by
node to neighbor to edge keys to edge data for multi-edges.
A NetworkXError is raised if this is not the case.
If False, :func:`to_networkx_graph` is used to try to determine
the dict's graph data structure as either a dict-of-dict-of-dict
keyed by node to neighbor to edge data, or a dict-of-iterable
keyed by node to neighbors.
If None, the treatment for True is tried, but if it fails,
the treatment for False is tried.
attr : keyword arguments, optional (default= no attributes)
Attributes to add to graph as key=value pairs.
See Also
--------
convert
Examples
--------
>>> G = nx.MultiGraph()
>>> G = nx.MultiGraph(name="my graph")
>>> e = [(1, 2), (1, 2), (2, 3), (3, 4)] # list of edges
>>> G = nx.MultiGraph(e)
Arbitrary graph attribute pairs (key=value) may be assigned
>>> G = nx.MultiGraph(e, day="Friday")
>>> G.graph
{'day': 'Friday'}
"""
# multigraph_input can be None/True/False. So check "is not False"
if isinstance(incoming_graph_data, dict) and multigraph_input is not False:
Graph.__init__(self)
try:
convert.from_dict_of_dicts(
incoming_graph_data, create_using=self, multigraph_input=True
)
self.graph.update(attr)
except Exception as err:
if multigraph_input is True:
raise nx.NetworkXError(
f"converting multigraph_input raised:\n{type(err)}: {err}"
)
Graph.__init__(self, incoming_graph_data, **attr)
else:
Graph.__init__(self, incoming_graph_data, **attr)
@cached_property
def adj(self):
"""Graph adjacency object holding the neighbors of each node.
This object is a read-only dict-like structure with node keys
and neighbor-dict values. The neighbor-dict is keyed by neighbor
to the edgekey-data-dict. So `G.adj[3][2][0]['color'] = 'blue'` sets
the color of the edge `(3, 2, 0)` to `"blue"`.
Iterating over G.adj behaves like a dict. Useful idioms include
`for nbr, edgesdict in G.adj[n].items():`.
The neighbor information is also provided by subscripting the graph.
Examples
--------
>>> e = [(1, 2), (1, 2), (1, 3), (3, 4)] # list of edges
>>> G = nx.MultiGraph(e)
>>> G.edges[1, 2, 0]["weight"] = 3
>>> result = set()
>>> for edgekey, data in G[1][2].items():
... result.add(data.get("weight", 1))
>>> result
{1, 3}
For directed graphs, `G.adj` holds outgoing (successor) info.
"""
return MultiAdjacencyView(self._adj)
def new_edge_key(self, u, v):
"""Returns an unused key for edges between nodes `u` and `v`.
The nodes `u` and `v` do not need to be already in the graph.
Notes
-----
In the standard MultiGraph class the new key is the number of existing
edges between `u` and `v` (increased if necessary to ensure unused).
The first edge will have key 0, then 1, etc. If an edge is removed
further new_edge_keys may not be in this order.
Parameters
----------
u, v : nodes
Returns
-------
key : int
"""
try:
keydict = self._adj[u][v]
except KeyError:
return 0
key = len(keydict)
while key in keydict:
key += 1
return key
def add_edge(self, u_for_edge, v_for_edge, key=None, **attr):
"""Add an edge between u and v.
The nodes u and v will be automatically added if they are
not already in the graph.
Edge attributes can be specified with keywords or by directly
accessing the edge's attribute dictionary. See examples below.
Parameters
----------
u_for_edge, v_for_edge : nodes
Nodes can be, for example, strings or numbers.
Nodes must be hashable (and not None) Python objects.
key : hashable identifier, optional (default=lowest unused integer)
Used to distinguish multiedges between a pair of nodes.
attr : keyword arguments, optional
Edge data (or labels or objects) can be assigned using
keyword arguments.
Returns
-------
The edge key assigned to the edge.
See Also
--------
add_edges_from : add a collection of edges
Notes
-----
To replace/update edge data, use the optional key argument
to identify a unique edge. Otherwise a new edge will be created.
NetworkX algorithms designed for weighted graphs cannot use
multigraphs directly because it is not clear how to handle
multiedge weights. Convert to Graph using edge attribute
'weight' to enable weighted graph algorithms.
Default keys are generated using the method `new_edge_key()`.
This method can be overridden by subclassing the base class and
providing a custom `new_edge_key()` method.
Examples
--------
The following each add an additional edge e=(1, 2) to graph G:
>>> G = nx.MultiGraph()
>>> e = (1, 2)
>>> ekey = G.add_edge(1, 2) # explicit two-node form
>>> G.add_edge(*e) # single edge as tuple of two nodes
1
>>> G.add_edges_from([(1, 2)]) # add edges from iterable container
[2]
Associate data to edges using keywords:
>>> ekey = G.add_edge(1, 2, weight=3)
>>> ekey = G.add_edge(1, 2, key=0, weight=4) # update data for key=0
>>> ekey = G.add_edge(1, 3, weight=7, capacity=15, length=342.7)
For non-string attribute keys, use subscript notation.
>>> ekey = G.add_edge(1, 2)
>>> G[1][2][0].update({0: 5})
>>> G.edges[1, 2, 0].update({0: 5})
"""
u, v = u_for_edge, v_for_edge
# add nodes
if u not in self._adj:
if u is None:
raise ValueError("None cannot be a node")
self._adj[u] = self.adjlist_inner_dict_factory()
self._node[u] = self.node_attr_dict_factory()
if v not in self._adj:
if v is None:
raise ValueError("None cannot be a node")
self._adj[v] = self.adjlist_inner_dict_factory()
self._node[v] = self.node_attr_dict_factory()
if key is None:
key = self.new_edge_key(u, v)
if v in self._adj[u]:
keydict = self._adj[u][v]
datadict = keydict.get(key, self.edge_attr_dict_factory())
datadict.update(attr)
keydict[key] = datadict
else:
# selfloops work this way without special treatment
datadict = self.edge_attr_dict_factory()
datadict.update(attr)
keydict = self.edge_key_dict_factory()
keydict[key] = datadict
self._adj[u][v] = keydict
self._adj[v][u] = keydict
nx._clear_cache(self)
return key
def add_edges_from(self, ebunch_to_add, **attr):
"""Add all the edges in ebunch_to_add.
Parameters
----------
ebunch_to_add : container of edges
Each edge given in the container will be added to the
graph. The edges can be:
- 2-tuples (u, v) or
- 3-tuples (u, v, d) for an edge data dict d, or
- 3-tuples (u, v, k) for not iterable key k, or
- 4-tuples (u, v, k, d) for an edge with data and key k
attr : keyword arguments, optional
Edge data (or labels or objects) can be assigned using
keyword arguments.
Returns
-------
A list of edge keys assigned to the edges in `ebunch`.
See Also
--------
add_edge : add a single edge
add_weighted_edges_from : convenient way to add weighted edges
Notes
-----
Adding the same edge twice has no effect but any edge data
will be updated when each duplicate edge is added.
Edge attributes specified in an ebunch take precedence over
attributes specified via keyword arguments.
Default keys are generated using the method ``new_edge_key()``.
This method can be overridden by subclassing the base class and
providing a custom ``new_edge_key()`` method.
When adding edges from an iterator over the graph you are changing,
a `RuntimeError` can be raised with message:
`RuntimeError: dictionary changed size during iteration`. This
happens when the graph's underlying dictionary is modified during
iteration. To avoid this error, evaluate the iterator into a separate
object, e.g. by using `list(iterator_of_edges)`, and pass this
object to `G.add_edges_from`.
Examples
--------
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.add_edges_from([(0, 1), (1, 2)]) # using a list of edge tuples
>>> e = zip(range(0, 3), range(1, 4))
>>> G.add_edges_from(e) # Add the path graph 0-1-2-3
Associate data to edges
>>> G.add_edges_from([(1, 2), (2, 3)], weight=3)
>>> G.add_edges_from([(3, 4), (1, 4)], label="WN2898")
Evaluate an iterator over a graph if using it to modify the same graph
>>> G = nx.MultiGraph([(1, 2), (2, 3), (3, 4)])
>>> # Grow graph by one new node, adding edges to all existing nodes.
>>> # wrong way - will raise RuntimeError
>>> # G.add_edges_from(((5, n) for n in G.nodes))
>>> # right way - note that there will be no self-edge for node 5
>>> assigned_keys = G.add_edges_from(list((5, n) for n in G.nodes))
"""
keylist = []
for e in ebunch_to_add:
ne = len(e)
if ne == 4:
u, v, key, dd = e
elif ne == 3:
u, v, dd = e
key = None
elif ne == 2:
u, v = e
dd = {}
key = None
else:
msg = f"Edge tuple {e} must be a 2-tuple, 3-tuple or 4-tuple."
raise NetworkXError(msg)
ddd = {}
ddd.update(attr)
try:
ddd.update(dd)
except (TypeError, ValueError):
if ne != 3:
raise
key = dd # ne == 3 with 3rd value not dict, must be a key
key = self.add_edge(u, v, key)
self[u][v][key].update(ddd)
keylist.append(key)
nx._clear_cache(self)
return keylist
def remove_edge(self, u, v, key=None):
"""Remove an edge between u and v.
Parameters
----------
u, v : nodes
Remove an edge between nodes u and v.
key : hashable identifier, optional (default=None)
Used to distinguish multiple edges between a pair of nodes.
If None, remove a single edge between u and v. If there are
multiple edges, removes the last edge added in terms of
insertion order.
Raises
------
NetworkXError
If there is not an edge between u and v, or
if there is no edge with the specified key.
See Also
--------
remove_edges_from : remove a collection of edges
Examples
--------
>>> G = nx.MultiGraph()
>>> nx.add_path(G, [0, 1, 2, 3])
>>> G.remove_edge(0, 1)
>>> e = (1, 2)
>>> G.remove_edge(*e) # unpacks e from an edge tuple
For multiple edges
>>> G = nx.MultiGraph() # or MultiDiGraph, etc
>>> G.add_edges_from([(1, 2), (1, 2), (1, 2)]) # key_list returned
[0, 1, 2]
When ``key=None`` (the default), edges are removed in the opposite
order that they were added:
>>> G.remove_edge(1, 2)
>>> G.edges(keys=True)
MultiEdgeView([(1, 2, 0), (1, 2, 1)])
>>> G.remove_edge(2, 1) # edges are not directed
>>> G.edges(keys=True)
MultiEdgeView([(1, 2, 0)])
For edges with keys
>>> G = nx.MultiGraph()
>>> G.add_edge(1, 2, key="first")
'first'
>>> G.add_edge(1, 2, key="second")
'second'
>>> G.remove_edge(1, 2, key="first")
>>> G.edges(keys=True)
MultiEdgeView([(1, 2, 'second')])
"""
try:
d = self._adj[u][v]
except KeyError as err:
raise NetworkXError(f"The edge {u}-{v} is not in the graph.") from err
# remove the edge with specified data
if key is None:
d.popitem()
else:
try:
del d[key]
except KeyError as err:
msg = f"The edge {u}-{v} with key {key} is not in the graph."
raise NetworkXError(msg) from err
if len(d) == 0:
# remove the key entries if last edge
del self._adj[u][v]
if u != v: # check for selfloop
del self._adj[v][u]
nx._clear_cache(self)
def remove_edges_from(self, ebunch):
"""Remove all edges specified in ebunch.
Parameters
----------
ebunch: list or container of edge tuples
Each edge given in the list or container will be removed
from the graph. The edges can be:
- 2-tuples (u, v) A single edge between u and v is removed.
- 3-tuples (u, v, key) The edge identified by key is removed.
- 4-tuples (u, v, key, data) where data is ignored.
See Also
--------
remove_edge : remove a single edge
Notes
-----
Will fail silently if an edge in ebunch is not in the graph.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> ebunch = [(1, 2), (2, 3)]
>>> G.remove_edges_from(ebunch)
Removing multiple copies of edges
>>> G = nx.MultiGraph()
>>> keys = G.add_edges_from([(1, 2), (1, 2), (1, 2)])
>>> G.remove_edges_from([(1, 2), (2, 1)]) # edges aren't directed
>>> list(G.edges())
[(1, 2)]
>>> G.remove_edges_from([(1, 2), (1, 2)]) # silently ignore extra copy
>>> list(G.edges) # now empty graph
[]
When the edge is a 2-tuple ``(u, v)`` but there are multiple edges between
u and v in the graph, the most recent edge (in terms of insertion
order) is removed.
>>> G = nx.MultiGraph()
>>> for key in ("x", "y", "a"):
... k = G.add_edge(0, 1, key=key)
>>> G.edges(keys=True)
MultiEdgeView([(0, 1, 'x'), (0, 1, 'y'), (0, 1, 'a')])
>>> G.remove_edges_from([(0, 1)])
>>> G.edges(keys=True)
MultiEdgeView([(0, 1, 'x'), (0, 1, 'y')])
"""
for e in ebunch:
try:
self.remove_edge(*e[:3])
except NetworkXError:
pass
nx._clear_cache(self)
def has_edge(self, u, v, key=None):
"""Returns True if the graph has an edge between nodes u and v.
This is the same as `v in G[u] or key in G[u][v]`
without KeyError exceptions.
Parameters
----------
u, v : nodes
Nodes can be, for example, strings or numbers.
key : hashable identifier, optional (default=None)
If specified return True only if the edge with
key is found.
Returns
-------
edge_ind : bool
True if edge is in the graph, False otherwise.
Examples
--------
Can be called either using two nodes u, v, an edge tuple (u, v),
or an edge tuple (u, v, key).
>>> G = nx.MultiGraph() # or MultiDiGraph
>>> nx.add_path(G, [0, 1, 2, 3])
>>> G.has_edge(0, 1) # using two nodes
True
>>> e = (0, 1)
>>> G.has_edge(*e) # e is a 2-tuple (u, v)
True
>>> G.add_edge(0, 1, key="a")
'a'
>>> G.has_edge(0, 1, key="a") # specify key
True
>>> G.has_edge(1, 0, key="a") # edges aren't directed
True
>>> e = (0, 1, "a")
>>> G.has_edge(*e) # e is a 3-tuple (u, v, 'a')
True
The following syntax are equivalent:
>>> G.has_edge(0, 1)
True
>>> 1 in G[0] # though this gives :exc:`KeyError` if 0 not in G
True
>>> 0 in G[1] # other order; also gives :exc:`KeyError` if 0 not in G
True
"""
try:
if key is None:
return v in self._adj[u]
else:
return key in self._adj[u][v]
except KeyError:
return False
@cached_property
def edges(self):
"""Returns an iterator over the edges.
edges(self, nbunch=None, data=False, keys=False, default=None)
The MultiEdgeView provides set-like operations on the edge-tuples
as well as edge attribute lookup. When called, it also provides
an EdgeDataView object which allows control of access to edge
attributes (but does not provide set-like operations).
Hence, ``G.edges[u, v, k]['color']`` provides the value of the color
attribute for the edge from ``u`` to ``v`` with key ``k`` while
``for (u, v, k, c) in G.edges(data='color', keys=True, default="red"):``
iterates through all the edges yielding the color attribute with
default `'red'` if no color attribute exists.
Edges are returned as tuples with optional data and keys
in the order (node, neighbor, key, data). If ``keys=True`` is not
provided, the tuples will just be (node, neighbor, data), but
multiple tuples with the same node and neighbor will be generated
when multiple edges exist between two nodes.
Parameters
----------
nbunch : single node, container, or all nodes (default= all nodes)
The view will only report edges from these nodes.
data : string or bool, optional (default=False)
The edge attribute returned in 3-tuple (u, v, ddict[data]).
If True, return edge attribute dict in 3-tuple (u, v, ddict).
If False, return 2-tuple (u, v).
keys : bool, optional (default=False)
If True, return edge keys with each edge, creating (u, v, k)
tuples or (u, v, k, d) tuples if data is also requested.
default : value, optional (default=None)
Value used for edges that don't have the requested attribute.
Only relevant if data is not True or False.
Returns
-------
edges : MultiEdgeView
A view of edge attributes, usually it iterates over (u, v)
(u, v, k) or (u, v, k, d) tuples of edges, but can also be
used for attribute lookup as ``edges[u, v, k]['foo']``.
Notes
-----
Nodes in nbunch that are not in the graph will be (quietly) ignored.
For directed graphs this returns the out-edges.
Examples
--------
>>> G = nx.MultiGraph()
>>> nx.add_path(G, [0, 1, 2])
>>> key = G.add_edge(2, 3, weight=5)
>>> key2 = G.add_edge(2, 1, weight=2) # multi-edge
>>> [e for e in G.edges()]
[(0, 1), (1, 2), (1, 2), (2, 3)]
>>> G.edges.data() # default data is {} (empty dict)
MultiEdgeDataView([(0, 1, {}), (1, 2, {}), (1, 2, {'weight': 2}), (2, 3, {'weight': 5})])
>>> G.edges.data("weight", default=1)
MultiEdgeDataView([(0, 1, 1), (1, 2, 1), (1, 2, 2), (2, 3, 5)])
>>> G.edges(keys=True) # default keys are integers
MultiEdgeView([(0, 1, 0), (1, 2, 0), (1, 2, 1), (2, 3, 0)])
>>> G.edges.data(keys=True)
MultiEdgeDataView([(0, 1, 0, {}), (1, 2, 0, {}), (1, 2, 1, {'weight': 2}), (2, 3, 0, {'weight': 5})])
>>> G.edges.data("weight", default=1, keys=True)
MultiEdgeDataView([(0, 1, 0, 1), (1, 2, 0, 1), (1, 2, 1, 2), (2, 3, 0, 5)])
>>> G.edges([0, 3]) # Note ordering of tuples from listed sources
MultiEdgeDataView([(0, 1), (3, 2)])
>>> G.edges([0, 3, 2, 1]) # Note ordering of tuples
MultiEdgeDataView([(0, 1), (3, 2), (2, 1), (2, 1)])
>>> G.edges(0)
MultiEdgeDataView([(0, 1)])
"""
return MultiEdgeView(self)
def get_edge_data(self, u, v, key=None, default=None):
"""Returns the attribute dictionary associated with edge (u, v,
key).
If a key is not provided, returns a dictionary mapping edge keys
to attribute dictionaries for each edge between u and v.
This is identical to `G[u][v][key]` except the default is returned
instead of an exception is the edge doesn't exist.
Parameters
----------
u, v : nodes
default : any Python object (default=None)
Value to return if the specific edge (u, v, key) is not
found, OR if there are no edges between u and v and no key
is specified.
key : hashable identifier, optional (default=None)
Return data only for the edge with specified key, as an
attribute dictionary (rather than a dictionary mapping keys
to attribute dictionaries).
Returns
-------
edge_dict : dictionary
The edge attribute dictionary, OR a dictionary mapping edge
keys to attribute dictionaries for each of those edges if no
specific key is provided (even if there's only one edge
between u and v).
Examples
--------
>>> G = nx.MultiGraph() # or MultiDiGraph
>>> key = G.add_edge(0, 1, key="a", weight=7)
>>> G[0][1]["a"] # key='a'
{'weight': 7}
>>> G.edges[0, 1, "a"] # key='a'
{'weight': 7}
Warning: we protect the graph data structure by making
`G.edges` and `G[1][2]` read-only dict-like structures.
However, you can assign values to attributes in e.g.
`G.edges[1, 2, 'a']` or `G[1][2]['a']` using an additional
bracket as shown next. You need to specify all edge info
to assign to the edge data associated with an edge.
>>> G[0][1]["a"]["weight"] = 10
>>> G.edges[0, 1, "a"]["weight"] = 10
>>> G[0][1]["a"]["weight"]
10
>>> G.edges[1, 0, "a"]["weight"]
10
>>> G = nx.MultiGraph() # or MultiDiGraph
>>> nx.add_path(G, [0, 1, 2, 3])
>>> G.edges[0, 1, 0]["weight"] = 5
>>> G.get_edge_data(0, 1)
{0: {'weight': 5}}
>>> e = (0, 1)
>>> G.get_edge_data(*e) # tuple form
{0: {'weight': 5}}
>>> G.get_edge_data(3, 0) # edge not in graph, returns None
>>> G.get_edge_data(3, 0, default=0) # edge not in graph, return default
0
>>> G.get_edge_data(1, 0, 0) # specific key gives back
{'weight': 5}
"""
try:
if key is None:
return self._adj[u][v]
else:
return self._adj[u][v][key]
except KeyError:
return default
@cached_property
def degree(self):
"""A DegreeView for the Graph as G.degree or G.degree().
The node degree is the number of edges adjacent to the node.
The weighted node degree is the sum of the edge weights for
edges incident to that node.
This object provides an iterator for (node, degree) as well as
lookup for the degree for a single node.
Parameters
----------
nbunch : single node, container, or all nodes (default= all nodes)
The view will only report edges incident to these nodes.
weight : string or None, optional (default=None)
The name of an edge attribute that holds the numerical value used
as a weight. If None, then each edge has weight 1.
The degree is the sum of the edge weights adjacent to the node.
Returns
-------
MultiDegreeView or int
If multiple nodes are requested (the default), returns a `MultiDegreeView`
mapping nodes to their degree.
If a single node is requested, returns the degree of the node as an integer.
Examples
--------
>>> G = nx.Graph() # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> nx.add_path(G, [0, 1, 2, 3])
>>> G.degree(0) # node 0 with degree 1
1
>>> list(G.degree([0, 1]))
[(0, 1), (1, 2)]
"""
return MultiDegreeView(self)
def is_multigraph(self):
"""Returns True if graph is a multigraph, False otherwise."""
return True
def is_directed(self):
"""Returns True if graph is directed, False otherwise."""
return False
def copy(self, as_view=False):
"""Returns a copy of the graph.
The copy method by default returns an independent shallow copy
of the graph and attributes. That is, if an attribute is a
container, that container is shared by the original an the copy.
Use Python's `copy.deepcopy` for new containers.
If `as_view` is True then a view is returned instead of a copy.
Notes
-----
All copies reproduce the graph structure, but data attributes
may be handled in different ways. There are four types of copies
of a graph that people might want.
Deepcopy -- A "deepcopy" copies the graph structure as well as
all data attributes and any objects they might contain.
The entire graph object is new so that changes in the copy
do not affect the original object. (see Python's copy.deepcopy)
Data Reference (Shallow) -- For a shallow copy the graph structure
is copied but the edge, node and graph attribute dicts are
references to those in the original graph. This saves
time and memory but could cause confusion if you change an attribute
in one graph and it changes the attribute in the other.
NetworkX does not provide this level of shallow copy.
Independent Shallow -- This copy creates new independent attribute
dicts and then does a shallow copy of the attributes. That is, any
attributes that are containers are shared between the new graph
and the original. This is exactly what `dict.copy()` provides.
You can obtain this style copy using:
>>> G = nx.path_graph(5)
>>> H = G.copy()
>>> H = G.copy(as_view=False)
>>> H = nx.Graph(G)
>>> H = G.__class__(G)
Fresh Data -- For fresh data, the graph structure is copied while
new empty data attribute dicts are created. The resulting graph
is independent of the original and it has no edge, node or graph
attributes. Fresh copies are not enabled. Instead use:
>>> H = G.__class__()
>>> H.add_nodes_from(G)
>>> H.add_edges_from(G.edges)
View -- Inspired by dict-views, graph-views act like read-only
versions of the original graph, providing a copy of the original
structure without requiring any memory for copying the information.
See the Python copy module for more information on shallow
and deep copies, https://docs.python.org/3/library/copy.html.
Parameters
----------
as_view : bool, optional (default=False)
If True, the returned graph-view provides a read-only view
of the original graph without actually copying any data.
Returns
-------
G : Graph
A copy of the graph.
See Also
--------
to_directed: return a directed copy of the graph.
Examples
--------
>>> G = nx.path_graph(4) # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> H = G.copy()
"""
if as_view is True:
return nx.graphviews.generic_graph_view(self)
G = self.__class__()
G.graph.update(self.graph)
G.add_nodes_from((n, d.copy()) for n, d in self._node.items())
G.add_edges_from(
(u, v, key, datadict.copy())
for u, nbrs in self._adj.items()
for v, keydict in nbrs.items()
for key, datadict in keydict.items()
)
return G
def to_directed(self, as_view=False):
"""Returns a directed representation of the graph.
Returns
-------
G : MultiDiGraph
A directed graph with the same name, same nodes, and with
each edge (u, v, k, data) replaced by two directed edges
(u, v, k, data) and (v, u, k, data).
Notes
-----
This returns a "deepcopy" of the edge, node, and
graph attributes which attempts to completely copy
all of the data and references.
This is in contrast to the similar D=MultiDiGraph(G) which
returns a shallow copy of the data.
See the Python copy module for more information on shallow
and deep copies, https://docs.python.org/3/library/copy.html.
Warning: If you have subclassed MultiGraph to use dict-like objects
in the data structure, those changes do not transfer to the
MultiDiGraph created by this method.
Examples
--------
>>> G = nx.MultiGraph()
>>> G.add_edge(0, 1)
0
>>> G.add_edge(0, 1)
1
>>> H = G.to_directed()
>>> list(H.edges)
[(0, 1, 0), (0, 1, 1), (1, 0, 0), (1, 0, 1)]
If already directed, return a (deep) copy
>>> G = nx.MultiDiGraph()
>>> G.add_edge(0, 1)
0
>>> H = G.to_directed()
>>> list(H.edges)
[(0, 1, 0)]
"""
graph_class = self.to_directed_class()
if as_view is True:
return nx.graphviews.generic_graph_view(self, graph_class)
# deepcopy when not a view
G = graph_class()
G.graph.update(deepcopy(self.graph))
G.add_nodes_from((n, deepcopy(d)) for n, d in self._node.items())
G.add_edges_from(
(u, v, key, deepcopy(datadict))
for u, nbrs in self.adj.items()
for v, keydict in nbrs.items()
for key, datadict in keydict.items()
)
return G
def to_undirected(self, as_view=False):
"""Returns an undirected copy of the graph.
Returns
-------
G : Graph/MultiGraph
A deepcopy of the graph.
See Also
--------
copy, add_edge, add_edges_from
Notes
-----
This returns a "deepcopy" of the edge, node, and
graph attributes which attempts to completely copy
all of the data and references.
This is in contrast to the similar `G = nx.MultiGraph(D)`
which returns a shallow copy of the data.
See the Python copy module for more information on shallow
and deep copies, https://docs.python.org/3/library/copy.html.
Warning: If you have subclassed MultiGraph to use dict-like
objects in the data structure, those changes do not transfer
to the MultiGraph created by this method.
Examples
--------
>>> G = nx.MultiGraph([(0, 1), (0, 1), (1, 2)])
>>> H = G.to_directed()
>>> list(H.edges)
[(0, 1, 0), (0, 1, 1), (1, 0, 0), (1, 0, 1), (1, 2, 0), (2, 1, 0)]
>>> G2 = H.to_undirected()
>>> list(G2.edges)
[(0, 1, 0), (0, 1, 1), (1, 2, 0)]
"""
graph_class = self.to_undirected_class()
if as_view is True:
return nx.graphviews.generic_graph_view(self, graph_class)
# deepcopy when not a view
G = graph_class()
G.graph.update(deepcopy(self.graph))
G.add_nodes_from((n, deepcopy(d)) for n, d in self._node.items())
G.add_edges_from(
(u, v, key, deepcopy(datadict))
for u, nbrs in self._adj.items()
for v, keydict in nbrs.items()
for key, datadict in keydict.items()
)
return G
def number_of_edges(self, u=None, v=None):
"""Returns the number of edges between two nodes.
Parameters
----------
u, v : nodes, optional (Default=all edges)
If u and v are specified, return the number of edges between
u and v. Otherwise return the total number of all edges.
Returns
-------
nedges : int
The number of edges in the graph. If nodes `u` and `v` are
specified return the number of edges between those nodes. If
the graph is directed, this only returns the number of edges
from `u` to `v`.
See Also
--------
size
Examples
--------
For undirected multigraphs, this method counts the total number
of edges in the graph::
>>> G = nx.MultiGraph()
>>> G.add_edges_from([(0, 1), (0, 1), (1, 2)])
[0, 1, 0]
>>> G.number_of_edges()
3
If you specify two nodes, this counts the total number of edges
joining the two nodes::
>>> G.number_of_edges(0, 1)
2
For directed multigraphs, this method can count the total number
of directed edges from `u` to `v`::
>>> G = nx.MultiDiGraph()
>>> G.add_edges_from([(0, 1), (0, 1), (1, 0)])
[0, 1, 0]
>>> G.number_of_edges(0, 1)
2
>>> G.number_of_edges(1, 0)
1
"""
if u is None:
return self.size()
try:
edgedata = self._adj[u][v]
except KeyError:
return 0 # no such edge
return len(edgedata)
| (incoming_graph_data=None, multigraph_input=None, **attr) |
30,223 | networkx.classes.multigraph | __init__ | Initialize a graph with edges, name, or graph attributes.
Parameters
----------
incoming_graph_data : input graph
Data to initialize graph. If incoming_graph_data=None (default)
an empty graph is created. The data can be an edge list, or any
NetworkX graph object. If the corresponding optional Python
packages are installed the data can also be a 2D NumPy array, a
SciPy sparse array, or a PyGraphviz graph.
multigraph_input : bool or None (default None)
Note: Only used when `incoming_graph_data` is a dict.
If True, `incoming_graph_data` is assumed to be a
dict-of-dict-of-dict-of-dict structure keyed by
node to neighbor to edge keys to edge data for multi-edges.
A NetworkXError is raised if this is not the case.
If False, :func:`to_networkx_graph` is used to try to determine
the dict's graph data structure as either a dict-of-dict-of-dict
keyed by node to neighbor to edge data, or a dict-of-iterable
keyed by node to neighbors.
If None, the treatment for True is tried, but if it fails,
the treatment for False is tried.
attr : keyword arguments, optional (default= no attributes)
Attributes to add to graph as key=value pairs.
See Also
--------
convert
Examples
--------
>>> G = nx.MultiGraph()
>>> G = nx.MultiGraph(name="my graph")
>>> e = [(1, 2), (1, 2), (2, 3), (3, 4)] # list of edges
>>> G = nx.MultiGraph(e)
Arbitrary graph attribute pairs (key=value) may be assigned
>>> G = nx.MultiGraph(e, day="Friday")
>>> G.graph
{'day': 'Friday'}
| def __init__(self, incoming_graph_data=None, multigraph_input=None, **attr):
"""Initialize a graph with edges, name, or graph attributes.
Parameters
----------
incoming_graph_data : input graph
Data to initialize graph. If incoming_graph_data=None (default)
an empty graph is created. The data can be an edge list, or any
NetworkX graph object. If the corresponding optional Python
packages are installed the data can also be a 2D NumPy array, a
SciPy sparse array, or a PyGraphviz graph.
multigraph_input : bool or None (default None)
Note: Only used when `incoming_graph_data` is a dict.
If True, `incoming_graph_data` is assumed to be a
dict-of-dict-of-dict-of-dict structure keyed by
node to neighbor to edge keys to edge data for multi-edges.
A NetworkXError is raised if this is not the case.
If False, :func:`to_networkx_graph` is used to try to determine
the dict's graph data structure as either a dict-of-dict-of-dict
keyed by node to neighbor to edge data, or a dict-of-iterable
keyed by node to neighbors.
If None, the treatment for True is tried, but if it fails,
the treatment for False is tried.
attr : keyword arguments, optional (default= no attributes)
Attributes to add to graph as key=value pairs.
See Also
--------
convert
Examples
--------
>>> G = nx.MultiGraph()
>>> G = nx.MultiGraph(name="my graph")
>>> e = [(1, 2), (1, 2), (2, 3), (3, 4)] # list of edges
>>> G = nx.MultiGraph(e)
Arbitrary graph attribute pairs (key=value) may be assigned
>>> G = nx.MultiGraph(e, day="Friday")
>>> G.graph
{'day': 'Friday'}
"""
# multigraph_input can be None/True/False. So check "is not False"
if isinstance(incoming_graph_data, dict) and multigraph_input is not False:
Graph.__init__(self)
try:
convert.from_dict_of_dicts(
incoming_graph_data, create_using=self, multigraph_input=True
)
self.graph.update(attr)
except Exception as err:
if multigraph_input is True:
raise nx.NetworkXError(
f"converting multigraph_input raised:\n{type(err)}: {err}"
)
Graph.__init__(self, incoming_graph_data, **attr)
else:
Graph.__init__(self, incoming_graph_data, **attr)
| (self, incoming_graph_data=None, multigraph_input=None, **attr) |
30,227 | networkx.classes.multigraph | add_edge | Add an edge between u and v.
The nodes u and v will be automatically added if they are
not already in the graph.
Edge attributes can be specified with keywords or by directly
accessing the edge's attribute dictionary. See examples below.
Parameters
----------
u_for_edge, v_for_edge : nodes
Nodes can be, for example, strings or numbers.
Nodes must be hashable (and not None) Python objects.
key : hashable identifier, optional (default=lowest unused integer)
Used to distinguish multiedges between a pair of nodes.
attr : keyword arguments, optional
Edge data (or labels or objects) can be assigned using
keyword arguments.
Returns
-------
The edge key assigned to the edge.
See Also
--------
add_edges_from : add a collection of edges
Notes
-----
To replace/update edge data, use the optional key argument
to identify a unique edge. Otherwise a new edge will be created.
NetworkX algorithms designed for weighted graphs cannot use
multigraphs directly because it is not clear how to handle
multiedge weights. Convert to Graph using edge attribute
'weight' to enable weighted graph algorithms.
Default keys are generated using the method `new_edge_key()`.
This method can be overridden by subclassing the base class and
providing a custom `new_edge_key()` method.
Examples
--------
The following each add an additional edge e=(1, 2) to graph G:
>>> G = nx.MultiGraph()
>>> e = (1, 2)
>>> ekey = G.add_edge(1, 2) # explicit two-node form
>>> G.add_edge(*e) # single edge as tuple of two nodes
1
>>> G.add_edges_from([(1, 2)]) # add edges from iterable container
[2]
Associate data to edges using keywords:
>>> ekey = G.add_edge(1, 2, weight=3)
>>> ekey = G.add_edge(1, 2, key=0, weight=4) # update data for key=0
>>> ekey = G.add_edge(1, 3, weight=7, capacity=15, length=342.7)
For non-string attribute keys, use subscript notation.
>>> ekey = G.add_edge(1, 2)
>>> G[1][2][0].update({0: 5})
>>> G.edges[1, 2, 0].update({0: 5})
| def add_edge(self, u_for_edge, v_for_edge, key=None, **attr):
"""Add an edge between u and v.
The nodes u and v will be automatically added if they are
not already in the graph.
Edge attributes can be specified with keywords or by directly
accessing the edge's attribute dictionary. See examples below.
Parameters
----------
u_for_edge, v_for_edge : nodes
Nodes can be, for example, strings or numbers.
Nodes must be hashable (and not None) Python objects.
key : hashable identifier, optional (default=lowest unused integer)
Used to distinguish multiedges between a pair of nodes.
attr : keyword arguments, optional
Edge data (or labels or objects) can be assigned using
keyword arguments.
Returns
-------
The edge key assigned to the edge.
See Also
--------
add_edges_from : add a collection of edges
Notes
-----
To replace/update edge data, use the optional key argument
to identify a unique edge. Otherwise a new edge will be created.
NetworkX algorithms designed for weighted graphs cannot use
multigraphs directly because it is not clear how to handle
multiedge weights. Convert to Graph using edge attribute
'weight' to enable weighted graph algorithms.
Default keys are generated using the method `new_edge_key()`.
This method can be overridden by subclassing the base class and
providing a custom `new_edge_key()` method.
Examples
--------
The following each add an additional edge e=(1, 2) to graph G:
>>> G = nx.MultiGraph()
>>> e = (1, 2)
>>> ekey = G.add_edge(1, 2) # explicit two-node form
>>> G.add_edge(*e) # single edge as tuple of two nodes
1
>>> G.add_edges_from([(1, 2)]) # add edges from iterable container
[2]
Associate data to edges using keywords:
>>> ekey = G.add_edge(1, 2, weight=3)
>>> ekey = G.add_edge(1, 2, key=0, weight=4) # update data for key=0
>>> ekey = G.add_edge(1, 3, weight=7, capacity=15, length=342.7)
For non-string attribute keys, use subscript notation.
>>> ekey = G.add_edge(1, 2)
>>> G[1][2][0].update({0: 5})
>>> G.edges[1, 2, 0].update({0: 5})
"""
u, v = u_for_edge, v_for_edge
# add nodes
if u not in self._adj:
if u is None:
raise ValueError("None cannot be a node")
self._adj[u] = self.adjlist_inner_dict_factory()
self._node[u] = self.node_attr_dict_factory()
if v not in self._adj:
if v is None:
raise ValueError("None cannot be a node")
self._adj[v] = self.adjlist_inner_dict_factory()
self._node[v] = self.node_attr_dict_factory()
if key is None:
key = self.new_edge_key(u, v)
if v in self._adj[u]:
keydict = self._adj[u][v]
datadict = keydict.get(key, self.edge_attr_dict_factory())
datadict.update(attr)
keydict[key] = datadict
else:
# selfloops work this way without special treatment
datadict = self.edge_attr_dict_factory()
datadict.update(attr)
keydict = self.edge_key_dict_factory()
keydict[key] = datadict
self._adj[u][v] = keydict
self._adj[v][u] = keydict
nx._clear_cache(self)
return key
| (self, u_for_edge, v_for_edge, key=None, **attr) |
30,248 | networkx.classes.multigraph | remove_edge | Remove an edge between u and v.
Parameters
----------
u, v : nodes
Remove an edge between nodes u and v.
key : hashable identifier, optional (default=None)
Used to distinguish multiple edges between a pair of nodes.
If None, remove a single edge between u and v. If there are
multiple edges, removes the last edge added in terms of
insertion order.
Raises
------
NetworkXError
If there is not an edge between u and v, or
if there is no edge with the specified key.
See Also
--------
remove_edges_from : remove a collection of edges
Examples
--------
>>> G = nx.MultiGraph()
>>> nx.add_path(G, [0, 1, 2, 3])
>>> G.remove_edge(0, 1)
>>> e = (1, 2)
>>> G.remove_edge(*e) # unpacks e from an edge tuple
For multiple edges
>>> G = nx.MultiGraph() # or MultiDiGraph, etc
>>> G.add_edges_from([(1, 2), (1, 2), (1, 2)]) # key_list returned
[0, 1, 2]
When ``key=None`` (the default), edges are removed in the opposite
order that they were added:
>>> G.remove_edge(1, 2)
>>> G.edges(keys=True)
MultiEdgeView([(1, 2, 0), (1, 2, 1)])
>>> G.remove_edge(2, 1) # edges are not directed
>>> G.edges(keys=True)
MultiEdgeView([(1, 2, 0)])
For edges with keys
>>> G = nx.MultiGraph()
>>> G.add_edge(1, 2, key="first")
'first'
>>> G.add_edge(1, 2, key="second")
'second'
>>> G.remove_edge(1, 2, key="first")
>>> G.edges(keys=True)
MultiEdgeView([(1, 2, 'second')])
| def remove_edge(self, u, v, key=None):
"""Remove an edge between u and v.
Parameters
----------
u, v : nodes
Remove an edge between nodes u and v.
key : hashable identifier, optional (default=None)
Used to distinguish multiple edges between a pair of nodes.
If None, remove a single edge between u and v. If there are
multiple edges, removes the last edge added in terms of
insertion order.
Raises
------
NetworkXError
If there is not an edge between u and v, or
if there is no edge with the specified key.
See Also
--------
remove_edges_from : remove a collection of edges
Examples
--------
>>> G = nx.MultiGraph()
>>> nx.add_path(G, [0, 1, 2, 3])
>>> G.remove_edge(0, 1)
>>> e = (1, 2)
>>> G.remove_edge(*e) # unpacks e from an edge tuple
For multiple edges
>>> G = nx.MultiGraph() # or MultiDiGraph, etc
>>> G.add_edges_from([(1, 2), (1, 2), (1, 2)]) # key_list returned
[0, 1, 2]
When ``key=None`` (the default), edges are removed in the opposite
order that they were added:
>>> G.remove_edge(1, 2)
>>> G.edges(keys=True)
MultiEdgeView([(1, 2, 0), (1, 2, 1)])
>>> G.remove_edge(2, 1) # edges are not directed
>>> G.edges(keys=True)
MultiEdgeView([(1, 2, 0)])
For edges with keys
>>> G = nx.MultiGraph()
>>> G.add_edge(1, 2, key="first")
'first'
>>> G.add_edge(1, 2, key="second")
'second'
>>> G.remove_edge(1, 2, key="first")
>>> G.edges(keys=True)
MultiEdgeView([(1, 2, 'second')])
"""
try:
d = self._adj[u][v]
except KeyError as err:
raise NetworkXError(f"The edge {u}-{v} is not in the graph.") from err
# remove the edge with specified data
if key is None:
d.popitem()
else:
try:
del d[key]
except KeyError as err:
msg = f"The edge {u}-{v} with key {key} is not in the graph."
raise NetworkXError(msg) from err
if len(d) == 0:
# remove the key entries if last edge
del self._adj[u][v]
if u != v: # check for selfloop
del self._adj[v][u]
nx._clear_cache(self)
| (self, u, v, key=None) |
30,256 | networkx.classes.multigraph | to_undirected | Returns an undirected copy of the graph.
Returns
-------
G : Graph/MultiGraph
A deepcopy of the graph.
See Also
--------
copy, add_edge, add_edges_from
Notes
-----
This returns a "deepcopy" of the edge, node, and
graph attributes which attempts to completely copy
all of the data and references.
This is in contrast to the similar `G = nx.MultiGraph(D)`
which returns a shallow copy of the data.
See the Python copy module for more information on shallow
and deep copies, https://docs.python.org/3/library/copy.html.
Warning: If you have subclassed MultiGraph to use dict-like
objects in the data structure, those changes do not transfer
to the MultiGraph created by this method.
Examples
--------
>>> G = nx.MultiGraph([(0, 1), (0, 1), (1, 2)])
>>> H = G.to_directed()
>>> list(H.edges)
[(0, 1, 0), (0, 1, 1), (1, 0, 0), (1, 0, 1), (1, 2, 0), (2, 1, 0)]
>>> G2 = H.to_undirected()
>>> list(G2.edges)
[(0, 1, 0), (0, 1, 1), (1, 2, 0)]
| def to_undirected(self, as_view=False):
"""Returns an undirected copy of the graph.
Returns
-------
G : Graph/MultiGraph
A deepcopy of the graph.
See Also
--------
copy, add_edge, add_edges_from
Notes
-----
This returns a "deepcopy" of the edge, node, and
graph attributes which attempts to completely copy
all of the data and references.
This is in contrast to the similar `G = nx.MultiGraph(D)`
which returns a shallow copy of the data.
See the Python copy module for more information on shallow
and deep copies, https://docs.python.org/3/library/copy.html.
Warning: If you have subclassed MultiGraph to use dict-like
objects in the data structure, those changes do not transfer
to the MultiGraph created by this method.
Examples
--------
>>> G = nx.MultiGraph([(0, 1), (0, 1), (1, 2)])
>>> H = G.to_directed()
>>> list(H.edges)
[(0, 1, 0), (0, 1, 1), (1, 0, 0), (1, 0, 1), (1, 2, 0), (2, 1, 0)]
>>> G2 = H.to_undirected()
>>> list(G2.edges)
[(0, 1, 0), (0, 1, 1), (1, 2, 0)]
"""
graph_class = self.to_undirected_class()
if as_view is True:
return nx.graphviews.generic_graph_view(self, graph_class)
# deepcopy when not a view
G = graph_class()
G.graph.update(deepcopy(self.graph))
G.add_nodes_from((n, deepcopy(d)) for n, d in self._node.items())
G.add_edges_from(
(u, v, key, deepcopy(datadict))
for u, nbrs in self._adj.items()
for v, keydict in nbrs.items()
for key, datadict in keydict.items()
)
return G
| (self, as_view=False) |
30,259 | networkx.exception | NetworkXAlgorithmError | Exception for unexpected termination of algorithms. | class NetworkXAlgorithmError(NetworkXException):
"""Exception for unexpected termination of algorithms."""
| null |
30,260 | networkx.exception | NetworkXError | Exception for a serious error in NetworkX | class NetworkXError(NetworkXException):
"""Exception for a serious error in NetworkX"""
| null |
30,261 | networkx.exception | NetworkXException | Base class for exceptions in NetworkX. | class NetworkXException(Exception):
"""Base class for exceptions in NetworkX."""
| null |
30,262 | networkx.exception | NetworkXNoCycle | Exception for algorithms that should return a cycle when running
on graphs where such a cycle does not exist. | class NetworkXNoCycle(NetworkXUnfeasible):
"""Exception for algorithms that should return a cycle when running
on graphs where such a cycle does not exist."""
| null |
30,263 | networkx.exception | NetworkXNoPath | Exception for algorithms that should return a path when running
on graphs where such a path does not exist. | class NetworkXNoPath(NetworkXUnfeasible):
"""Exception for algorithms that should return a path when running
on graphs where such a path does not exist."""
| null |
30,264 | networkx.exception | NetworkXNotImplemented | Exception raised by algorithms not implemented for a type of graph. | class NetworkXNotImplemented(NetworkXException):
"""Exception raised by algorithms not implemented for a type of graph."""
| null |
30,265 | networkx.exception | NetworkXPointlessConcept | Raised when a null graph is provided as input to an algorithm
that cannot use it.
The null graph is sometimes considered a pointless concept [1]_,
thus the name of the exception.
References
----------
.. [1] Harary, F. and Read, R. "Is the Null Graph a Pointless
Concept?" In Graphs and Combinatorics Conference, George
Washington University. New York: Springer-Verlag, 1973.
| class NetworkXPointlessConcept(NetworkXException):
"""Raised when a null graph is provided as input to an algorithm
that cannot use it.
The null graph is sometimes considered a pointless concept [1]_,
thus the name of the exception.
References
----------
.. [1] Harary, F. and Read, R. "Is the Null Graph a Pointless
Concept?" In Graphs and Combinatorics Conference, George
Washington University. New York: Springer-Verlag, 1973.
"""
| null |
30,266 | networkx.algorithms.chordal | NetworkXTreewidthBoundExceeded | Exception raised when a treewidth bound has been provided and it has
been exceeded | class NetworkXTreewidthBoundExceeded(nx.NetworkXException):
"""Exception raised when a treewidth bound has been provided and it has
been exceeded"""
| null |
30,267 | networkx.exception | NetworkXUnbounded | Exception raised by algorithms trying to solve a maximization
or a minimization problem instance that is unbounded. | class NetworkXUnbounded(NetworkXAlgorithmError):
"""Exception raised by algorithms trying to solve a maximization
or a minimization problem instance that is unbounded."""
| null |
30,268 | networkx.exception | NetworkXUnfeasible | Exception raised by algorithms trying to solve a problem
instance that has no feasible solution. | class NetworkXUnfeasible(NetworkXAlgorithmError):
"""Exception raised by algorithms trying to solve a problem
instance that has no feasible solution."""
| null |
30,269 | networkx.exception | NodeNotFound | Exception raised if requested node is not present in the graph | class NodeNotFound(NetworkXException):
"""Exception raised if requested node is not present in the graph"""
| null |
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