'Return the number of selfloop edges.
A selfloop edge has the same node at both ends.
Returns
nloops : int
The number of selfloops.
See Also
nodes_with_selfloops, selfloop_edges
Examples
>>> G = nx.Graph()   # or DiGraph, MultiGraph, MultiDiGraph, etc
>>> G.add_edge(1, 1)
>>> G.add_edge(1, 2)
>>> G.number_of_selfloops()
1'

def number_of_selfloops(self):

    return sum((1 for _ in self.selfloop_edges()))
