'Edits an existing item\'s attributes, or adds a new item to the
table if it does not already exist. You can put, delete, or
add attribute values. You can also perform a conditional
update (insert a new attribute name-value pair if it doesn\'t
exist, or replace an existing name-value pair if it has
certain expected attribute values).
You can also return the item\'s attribute values in the same
UpdateItem operation using the ReturnValues parameter.
:type table_name: string
:param table_name: The name of the table containing the item to update.
:type key: map
:param key: The primary key of the item to be updated. Each element
consists of an attribute name and a value for that attribute.
For the primary key, you must provide all of the attributes. For
example, with a hash type primary key, you only need to specify the
hash attribute. For a hash-and-range type primary key, you must
specify both the hash attribute and the range attribute.
:type attribute_updates: map
:param attribute_updates:
There is a newer parameter available. Use UpdateExpression instead.
Note that if you use AttributeUpdates and UpdateExpression at the
same time, DynamoDB will return a ValidationException exception.
This parameter can be used for modifying top-level attributes; however,
it does not support individual list or map elements.
The names of attributes to be modified, the action to perform on each,
and the new value for each. If you are updating an attribute that
is an index key attribute for any indexes on that table, the
attribute type must match the index key type defined in the
AttributesDefinition of the table description. You can use
UpdateItem to update any nonkey attributes.
Attribute values cannot be null. String and Binary type attributes must
have lengths greater than zero. Set type attributes must not be
empty. Requests with empty values will be rejected with a
ValidationException exception.
Each AttributeUpdates element consists of an attribute name to modify,
along with the following:
+ Value - The new value, if applicable, for this attribute.
+ Action - A value that specifies how to perform the update. This
action is only valid for an existing attribute whose data type is
Number or is a set; do not use `ADD` for other data types. If an
item with the specified primary key is found in the table, the
following values perform the following actions:
+ `PUT` - Adds the specified attribute to the item. If the attribute
already exists, it is replaced by the new value.
+ `DELETE` - Removes the attribute and its value, if no value is
specified for `DELETE`. The data type of the specified value must
match the existing value\'s data type. If a set of values is
specified, then those values are subtracted from the old set. For
example, if the attribute value was the set `[a,b,c]` and the
`DELETE` action specifies `[a,c]`, then the final attribute value
is `[b]`. Specifying an empty set is an error.
+ `ADD` - Adds the specified value to the item, if the attribute does
not already exist. If the attribute does exist, then the behavior
of `ADD` depends on the data type of the attribute:
+ If the existing attribute is a number, and if Value is also a number,
then Value is mathematically added to the existing attribute. If
Value is a negative number, then it is subtracted from the existing
attribute. If you use `ADD` to increment or decrement a number
value for an item that doesn\'t exist before the update, DynamoDB
uses 0 as the initial value. Similarly, if you use `ADD` for an
existing item to increment or decrement an attribute value that
doesn\'t exist before the update, DynamoDB uses `0` as the initial
value. For example, suppose that the item you want to update
doesn\'t have an attribute named itemcount , but you decide to `ADD`
the number `3` to this attribute anyway. DynamoDB will create the
itemcount attribute, set its initial value to `0`, and finally add
`3` to it. The result will be a new itemcount attribute, with a
value of `3`.
+ If the existing data type is a set, and if Value is also a set, then
Value is appended to the existing set. For example, if the
attribute value is the set `[1,2]`, and the `ADD` action specified
`[3]`, then the final attribute value is `[1,2,3]`. An error occurs
if an `ADD` action is specified for a set attribute and the
attribute type specified does not match the existing set type. Both
sets must have the same primitive data type. For example, if the
existing data type is a set of strings, Value must also be a set of
strings.
If no item with the specified key is found in the table, the following
values perform the following actions:
+ `PUT` - Causes DynamoDB to create a new item with the specified
primary key, and then adds the attribute.
+ `DELETE` - Nothing happens, because attributes cannot be deleted from
a nonexistent item. The operation succeeds, but DynamoDB does not
create a new item.
+ `ADD` - Causes DynamoDB to create an item with the supplied primary
key and number (or set of numbers) for the attribute value. The
only data types allowed are Number and Number Set.
If you specify any attributes that are part of an index key, then the
data types for those attributes must match those of the schema in
the table\'s attribute definition.
:type expected: map
:param expected:
There is a newer parameter available. Use ConditionExpression instead.
Note that if you use Expected and ConditionExpression at the same
time, DynamoDB will return a ValidationException exception.
This parameter does not support lists or maps.
A map of attribute/condition pairs. Expected provides a conditional
block for the UpdateItem operation.
Each element of Expected consists of an attribute name, a comparison
operator, and one or more values. DynamoDB compares the attribute
with the value(s) you supplied, using the comparison operator. For
each Expected element, the result of the evaluation is either true
or false.
If you specify more than one element in the Expected map, then by
default all of the conditions must evaluate to true. In other
words, the conditions are ANDed together. (You can use the
ConditionalOperator parameter to OR the conditions instead. If you
do this, then at least one of the conditions must evaluate to true,
rather than all of them.)
If the Expected map evaluates to true, then the conditional operation
succeeds; otherwise, it fails.
Expected contains the following:
+ AttributeValueList - One or more values to evaluate against the
supplied attribute. The number of values in the list depends on the
ComparisonOperator being used. For type Number, value comparisons
are numeric. String value comparisons for greater than, equals, or
less than are based on ASCII character code values. For example,
`a` is greater than `A`, and `a` is greater than `B`. For a list of
code values, see
`http://en.wikipedia.org/wiki/ASCII#ASCII_printable_characters`_.
For type Binary, DynamoDB treats each byte of the binary data as
unsigned when it compares binary values, for example when
evaluating query expressions.
+ ComparisonOperator - A comparator for evaluating attributes in the
AttributeValueList . When performing the comparison, DynamoDB uses
strongly consistent reads. The following comparison operators are
available: `EQ | NE | LE | LT | GE | GT | NOT_NULL | NULL |
CONTAINS | NOT_CONTAINS | BEGINS_WITH | IN | BETWEEN` The following
are descriptions of each comparison operator.
+ `EQ` : Equal. `EQ` is supported for all datatypes, including lists
and maps. AttributeValueList can contain only one AttributeValue
element of type String, Number, Binary, String Set, Number Set, or
Binary Set. If an item contains an AttributeValue element of a
different type than the one specified in the request, the value
does not match. For example, `{"S":"6"}` does not equal
`{"N":"6"}`. Also, `{"N":"6"}` does not equal `{"NS":["6", "2",
"1"]}`. > <li>
+ `NE` : Not equal. `NE` is supported for all datatypes, including
lists and maps. AttributeValueList can contain only one
AttributeValue of type String, Number, Binary, String Set, Number
Set, or Binary Set. If an item contains an AttributeValue of a
different type than the one specified in the request, the value
does not match. For example, `{"S":"6"}` does not equal
`{"N":"6"}`. Also, `{"N":"6"}` does not equal `{"NS":["6", "2",
"1"]}`. > <li>
+ `LE` : Less than or equal. AttributeValueList can contain only one
AttributeValue element of type String, Number, or Binary (not a set
type). If an item contains an AttributeValue element of a different
type than the one specified in the request, the value does not
match. For example, `{"S":"6"}` does not equal `{"N":"6"}`. Also,
`{"N":"6"}` does not compare to `{"NS":["6", "2", "1"]}`. > <li>
+ `LT` : Less than. AttributeValueList can contain only one
AttributeValue of type String, Number, or Binary (not a set type).
If an item contains an AttributeValue element of a different type
than the one specified in the request, the value does not match.
For example, `{"S":"6"}` does not equal `{"N":"6"}`. Also,
`{"N":"6"}` does not compare to `{"NS":["6", "2", "1"]}`. > <li>
+ `GE` : Greater than or equal. AttributeValueList can contain only one
AttributeValue element of type String, Number, or Binary (not a set
type). If an item contains an AttributeValue element of a different
type than the one specified in the request, the value does not
match. For example, `{"S":"6"}` does not equal `{"N":"6"}`. Also,
`{"N":"6"}` does not compare to `{"NS":["6", "2", "1"]}`. > <li>
+ `GT` : Greater than. AttributeValueList can contain only one
AttributeValue element of type String, Number, or Binary (not a set
type). If an item contains an AttributeValue element of a different
type than the one specified in the request, the value does not
match. For example, `{"S":"6"}` does not equal `{"N":"6"}`. Also,
`{"N":"6"}` does not compare to `{"NS":["6", "2", "1"]}`. > <li>
+ `NOT_NULL` : The attribute exists. `NOT_NULL` is supported for all
datatypes, including lists and maps. This operator tests for the
existence of an attribute, not its data type. If the data type of
attribute " `a`" is null, and you evaluate it using `NOT_NULL`, the
result is a Boolean true . This result is because the attribute "
`a`" exists; its data type is not relevant to the `NOT_NULL`
comparison operator.
+ `NULL` : The attribute does not exist. `NULL` is supported for all
datatypes, including lists and maps. This operator tests for the
nonexistence of an attribute, not its data type. If the data type
of attribute " `a`" is null, and you evaluate it using `NULL`, the
result is a Boolean false . This is because the attribute " `a`"
exists; its data type is not relevant to the `NULL` comparison
operator.
+ `CONTAINS` : Checks for a subsequence, or value in a set.
AttributeValueList can contain only one AttributeValue element of
type String, Number, or Binary (not a set type). If the target
attribute of the comparison is of type String, then the operator
checks for a substring match. If the target attribute of the
comparison is of type Binary, then the operator looks for a
subsequence of the target that matches the input. If the target
attribute of the comparison is a set (" `SS`", " `NS`", or "
`BS`"), then the operator evaluates to true if it finds an exact
match with any member of the set. CONTAINS is supported for lists:
When evaluating " `a CONTAINS b`", " `a`" can be a list; however, "
`b`" cannot be a set, a map, or a list.
+ `NOT_CONTAINS` : Checks for absence of a subsequence, or absence of a
value in a set. AttributeValueList can contain only one
AttributeValue element of type String, Number, or Binary (not a set
type). If the target attribute of the comparison is a String, then
the operator checks for the absence of a substring match. If the
target attribute of the comparison is Binary, then the operator
checks for the absence of a subsequence of the target that matches
the input. If the target attribute of the comparison is a set ("
`SS`", " `NS`", or " `BS`"), then the operator evaluates to true if
it does not find an exact match with any member of the set.
NOT_CONTAINS is supported for lists: When evaluating " `a NOT
CONTAINS b`", " `a`" can be a list; however, " `b`" cannot be a
set, a map, or a list.
+ `BEGINS_WITH` : Checks for a prefix. AttributeValueList can contain
only one AttributeValue of type String or Binary (not a Number or a
set type). The target attribute of the comparison must be of type
String or Binary (not a Number or a set type). > <li>
+ `IN` : Checks for matching elements within two sets.
AttributeValueList can contain one or more AttributeValue elements
of type String, Number, or Binary (not a set type). These
attributes are compared against an existing set type attribute of
an item. If any elements of the input set are present in the item
attribute, the expression evaluates to true.
+ `BETWEEN` : Greater than or equal to the first value, and less than
or equal to the second value. AttributeValueList must contain two
AttributeValue elements of the same type, either String, Number, or
Binary (not a set type). A target attribute matches if the target
value is greater than, or equal to, the first element and less
than, or equal to, the second element. If an item contains an
AttributeValue element of a different type than the one specified
in the request, the value does not match. For example, `{"S":"6"}`
does not compare to `{"N":"6"}`. Also, `{"N":"6"}` does not compare
to `{"NS":["6", "2", "1"]}`
For usage examples of AttributeValueList and ComparisonOperator , see
`Legacy Conditional Parameters`_ in the Amazon DynamoDB Developer
Guide .
For backward compatibility with previous DynamoDB releases, the
following parameters can be used instead of AttributeValueList and
ComparisonOperator :
+ Value - A value for DynamoDB to compare with an attribute.
+ Exists - A Boolean value that causes DynamoDB to evaluate the value
before attempting the conditional operation:
+ If Exists is `True`, DynamoDB will check to see if that attribute
value already exists in the table. If it is found, then the
condition evaluates to true; otherwise the condition evaluate to
false.
+ If Exists is `False`, DynamoDB assumes that the attribute value does
not exist in the table. If in fact the value does not exist, then
the assumption is valid and the condition evaluates to true. If the
value is found, despite the assumption that it does not exist, the
condition evaluates to false.
Note that the default value for Exists is `True`.
The Value and Exists parameters are incompatible with
AttributeValueList and ComparisonOperator . Note that if you use
both sets of parameters at once, DynamoDB will return a
ValidationException exception.
:type conditional_operator: string
:param conditional_operator:
There is a newer parameter available. Use ConditionExpression instead.
Note that if you use ConditionalOperator and ConditionExpression at
the same time, DynamoDB will return a ValidationException
exception.
This parameter does not support lists or maps.
A logical operator to apply to the conditions in the Expected map:
+ `AND` - If all of the conditions evaluate to true, then the entire
map evaluates to true.
+ `OR` - If at least one of the conditions evaluate to true, then the
entire map evaluates to true.
If you omit ConditionalOperator , then `AND` is the default.
The operation will succeed only if the entire map evaluates to true.
:type return_values: string
:param return_values:
Use ReturnValues if you want to get the item attributes as they
appeared either before or after they were updated. For UpdateItem ,
the valid values are:
+ `NONE` - If ReturnValues is not specified, or if its value is `NONE`,
then nothing is returned. (This setting is the default for
ReturnValues .)
+ `ALL_OLD` - If UpdateItem overwrote an attribute name-value pair,
then the content of the old item is returned.
+ `UPDATED_OLD` - The old versions of only the updated attributes are
returned.
+ `ALL_NEW` - All of the attributes of the new version of the item are
returned.
+ `UPDATED_NEW` - The new versions of only the updated attributes are
returned.
:type return_consumed_capacity: string
:param return_consumed_capacity: A value that if set to `TOTAL`, the
response includes ConsumedCapacity data for tables and indexes. If
set to `INDEXES`, the response includes ConsumedCapacity for
indexes. If set to `NONE` (the default), ConsumedCapacity is not
included in the response.
:type return_item_collection_metrics: string
:param return_item_collection_metrics: A value that if set to `SIZE`,
the response includes statistics about item collections, if any,
that were modified during the operation are returned in the
response. If set to `NONE` (the default), no statistics are
returned.
:type update_expression: string
:param update_expression: An expression that defines one or more
attributes to be updated, the action to be performed on them, and
new value(s) for them.
The following action values are available for UpdateExpression .
+ `SET` - Adds one or more attributes and values to an item. If any of
these attribute already exist, they are replaced by the new values.
You can also use `SET` to add or subtract from an attribute that is
of type Number. `SET` supports the following functions:
+ `if_not_exists (path, operand)` - if the item does not contain an
attribute at the specified path, then `if_not_exists` evaluates to
operand; otherwise, it evaluates to path. You can use this function
to avoid overwriting an attribute that may already be present in
the item.
+ `list_append (operand, operand)` - evaluates to a list with a new
element added to it. You can append the new element to the start or
the end of the list by reversing the order of the operands.
These function names are case-sensitive.
+ `REMOVE` - Removes one or more attributes from an item.
+ `ADD` - Adds the specified value to the item, if the attribute does
not already exist. If the attribute does exist, then the behavior
of `ADD` depends on the data type of the attribute:
+ If the existing attribute is a number, and if Value is also a number,
then Value is mathematically added to the existing attribute. If
Value is a negative number, then it is subtracted from the existing
attribute. If you use `ADD` to increment or decrement a number
value for an item that doesn\'t exist before the update, DynamoDB
uses `0` as the initial value. Similarly, if you use `ADD` for an
existing item to increment or decrement an attribute value that
doesn\'t exist before the update, DynamoDB uses `0` as the initial
value. For example, suppose that the item you want to update
doesn\'t have an attribute named itemcount , but you decide to `ADD`
the number `3` to this attribute anyway. DynamoDB will create the
itemcount attribute, set its initial value to `0`, and finally add
`3` to it. The result will be a new itemcount attribute in the
item, with a value of `3`.
+ If the existing data type is a set and if Value is also a set, then
Value is added to the existing set. For example, if the attribute
value is the set `[1,2]`, and the `ADD` action specified `[3]`,
then the final attribute value is `[1,2,3]`. An error occurs if an
`ADD` action is specified for a set attribute and the attribute
type specified does not match the existing set type. Both sets must
have the same primitive data type. For example, if the existing
data type is a set of strings, the Value must also be a set of
strings.
The `ADD` action only supports Number and set data types. In addition,
`ADD` can only be used on top-level attributes, not nested
attributes.
+ `DELETE` - Deletes an element from a set. If a set of values is
specified, then those values are subtracted from the old set. For
example, if the attribute value was the set `[a,b,c]` and the
`DELETE` action specifies `[a,c]`, then the final attribute value
is `[b]`. Specifying an empty set is an error. The `DELETE` action
only supports Number and set data types. In addition, `DELETE` can
only be used on top-level attributes, not nested attributes.
You can have many actions in a single expression, such as the
following: `SET a=:value1, b=:value2 DELETE :value3, :value4,
:value5`
For more information on update expressions, go to `Modifying Items and
Attributes`_ in the Amazon DynamoDB Developer Guide .
:type condition_expression: string
:param condition_expression: A condition that must be satisfied in
order for a conditional update to succeed.
An expression can contain any of the following:
+ Boolean functions: `attribute_exists | attribute_not_exists |
contains | begins_with` These function names are case-sensitive.
+ Comparison operators: ` = | <> | < | > | <=
| >= | BETWEEN | IN`
+ Logical operators: `AND | OR | NOT`
For more information on condition expressions, go to `Specifying
Conditions`_ in the Amazon DynamoDB Developer Guide .
:type expression_attribute_names: map
:param expression_attribute_names: One or more substitution tokens for
simplifying complex expressions. The following are some use cases
for using ExpressionAttributeNames :
+ To shorten an attribute name that is very long or unwieldy in an
expression.
+ To create a placeholder for repeating occurrences of an attribute
name in an expression.
+ To prevent special characters in an attribute name from being
misinterpreted in an expression.
Use the **#** character in an expression to dereference an attribute
name. For example, consider the following expression:
+ `order.customerInfo.LastName = "Smith" OR order.customerInfo.LastName
= "Jones"`
Now suppose that you specified the following for
ExpressionAttributeNames :
+ `{"#name":"order.customerInfo.LastName"}`
The expression can now be simplified as follows:
+ `#name = "Smith" OR #name = "Jones"`
For more information on expression attribute names, go to `Accessing
Item Attributes`_ in the Amazon DynamoDB Developer Guide .
:type expression_attribute_values: map
:param expression_attribute_values: One or more values that can be
substituted in an expression.
Use the **:** (colon) character in an expression to dereference an
attribute value. For example, suppose that you wanted to check
whether the value of the ProductStatus attribute was one of the
following:
`Available | Backordered | Discontinued`
You would first need to specify ExpressionAttributeValues as follows:
`{ ":avail":{"S":"Available"}, ":back":{"S":"Backordered"},
":disc":{"S":"Discontinued"} }`
You could then use these values in an expression, such as this:
`ProductStatus IN (:avail, :back, :disc)`
For more information on expression attribute values, go to `Specifying
Conditions`_ in the Amazon DynamoDB Developer Guide .'

def update_item(self, table_name, key, attribute_updates=None, expected=None, conditional_operator=None, return_values=None, return_consumed_capacity=None, return_item_collection_metrics=None, update_expression=None, condition_expression=None, expression_attribute_names=None, expression_attribute_values=None):

    params = {'TableName': table_name, 'Key': key}
    if (attribute_updates is not None):
        params['AttributeUpdates'] = attribute_updates
    if (expected is not None):
        params['Expected'] = expected
    if (conditional_operator is not None):
        params['ConditionalOperator'] = conditional_operator
    if (return_values is not None):
        params['ReturnValues'] = return_values
    if (return_consumed_capacity is not None):
        params['ReturnConsumedCapacity'] = return_consumed_capacity
    if (return_item_collection_metrics is not None):
        params['ReturnItemCollectionMetrics'] = return_item_collection_metrics
    if (update_expression is not None):
        params['UpdateExpression'] = update_expression
    if (condition_expression is not None):
        params['ConditionExpression'] = condition_expression
    if (expression_attribute_names is not None):
        params['ExpressionAttributeNames'] = expression_attribute_names
    if (expression_attribute_values is not None):
        params['ExpressionAttributeValues'] = expression_attribute_values
    return self.make_request(action='UpdateItem', body=json.dumps(params))
