'The Scan operation returns one or more items and item
attributes by accessing every item in the table. To have
DynamoDB return fewer items, you can provide a ScanFilter
operation.
If the total number of scanned items exceeds the maximum data
set size limit of 1 MB, the scan stops and results are
returned to the user as a LastEvaluatedKey value to continue
the scan in a subsequent operation. The results also include
the number of items exceeding the limit. A scan can result in
no table data meeting the filter criteria.
The result set is eventually consistent.
By default, Scan operations proceed sequentially; however, for
faster performance on large tables, applications can request a
parallel Scan operation by specifying the Segment and
TotalSegments parameters. For more information, see `Parallel
Scan`_ in the Amazon DynamoDB Developer Guide .
:type table_name: string
:param table_name: The name of the table containing the requested
items.
:type attributes_to_get: list
:param attributes_to_get:
There is a newer parameter available. Use ProjectionExpression instead.
Note that if you use AttributesToGet and ProjectionExpression at
the same time, DynamoDB will return a ValidationException
exception.
This parameter allows you to retrieve lists or maps; however, it cannot
retrieve individual list or map elements.
The names of one or more attributes to retrieve. If no attribute names
are specified, then all attributes will be returned. If any of the
requested attributes are not found, they will not appear in the
result.
Note that AttributesToGet has no effect on provisioned throughput
consumption. DynamoDB determines capacity units consumed based on
item size, not on the amount of data that is returned to an
application.
:type limit: integer
:param limit: The maximum number of items to evaluate (not necessarily
the number of matching items). If DynamoDB processes the number of
items up to the limit while processing the results, it stops the
operation and returns the matching values up to that point, and a
key in LastEvaluatedKey to apply in a subsequent operation, so that
you can pick up where you left off. Also, if the processed data set
size exceeds 1 MB before DynamoDB reaches this limit, it stops the
operation and returns the matching values up to the limit, and a
key in LastEvaluatedKey to apply in a subsequent operation to
continue the operation. For more information, see `Query and Scan`_
in the Amazon DynamoDB Developer Guide .
:type select: string
:param select: The attributes to be returned in the result. You can
retrieve all item attributes, specific item attributes, or the
count of matching items.
+ `ALL_ATTRIBUTES` - Returns all of the item attributes.
+ `COUNT` - Returns the number of matching items, rather than the
matching items themselves.
+ `SPECIFIC_ATTRIBUTES` - Returns only the attributes listed in
AttributesToGet . This return value is equivalent to specifying
AttributesToGet without specifying any value for Select .
If neither Select nor AttributesToGet are specified, DynamoDB defaults
to `ALL_ATTRIBUTES`. You cannot use both AttributesToGet and Select
together in a single request, unless the value for Select is
`SPECIFIC_ATTRIBUTES`. (This usage is equivalent to specifying
AttributesToGet without any value for Select .)
:type scan_filter: map
:param scan_filter:
There is a newer parameter available. Use FilterExpression instead.
Note that if you use ScanFilter and FilterExpression at the same
time, DynamoDB will return a ValidationException exception.
This parameter does not support lists or maps.
A condition that evaluates the scan results and returns only the
desired values.
If you specify more than one condition in the ScanFilter 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.)
Each ScanFilter element consists of an attribute name to compare, along
with the following:
+ AttributeValueList - One or more values to evaluate against the
supplied attribute. The number of values in the list depends on the
operator specified in ComparisonOperator . 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 Binary, DynamoDB treats each byte of the binary data as
unsigned when it compares binary values, for example when
evaluating query expressions. For information on specifying data
types in JSON, see `JSON Data Format`_ in the Amazon DynamoDB
Developer Guide .
+ ComparisonOperator - A comparator for evaluating attributes. For
example, equals, greater than, less than, etc. The following
comparison operators are available: `EQ | NE | LE | LT | GE | GT |
NOT_NULL | NULL | CONTAINS | NOT_CONTAINS | BEGINS_WITH | IN |
BETWEEN` For complete descriptions of all comparison operators, see
`Condition`_.
: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 ScanFilter 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 exclusive_start_key: map
:param exclusive_start_key: The primary key of the first item that this
operation will evaluate. Use the value that was returned for
LastEvaluatedKey in the previous operation.
The data type for ExclusiveStartKey must be String, Number or Binary.
No set data types are allowed.
In a parallel scan, a Scan request that includes ExclusiveStartKey must
specify the same segment whose previous Scan returned the
corresponding value of LastEvaluatedKey .
: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 total_segments: integer
:param total_segments: For a parallel Scan request, TotalSegments
represents the total number of segments into which the Scan
operation will be divided. The value of TotalSegments corresponds
to the number of application workers that will perform the parallel
scan. For example, if you want to scan a table using four
application threads, specify a TotalSegments value of 4.
The value for TotalSegments must be greater than or equal to 1, and
less than or equal to 1000000. If you specify a TotalSegments value
of 1, the Scan operation will be sequential rather than parallel.
If you specify TotalSegments , you must also specify Segment .
:type segment: integer
:param segment: For a parallel Scan request, Segment identifies an
individual segment to be scanned by an application worker.
Segment IDs are zero-based, so the first segment is always 0. For
example, if you want to scan a table using four application
threads, the first thread specifies a Segment value of 0, the
second thread specifies 1, and so on.
The value of LastEvaluatedKey returned from a parallel Scan request
must be used as ExclusiveStartKey with the same segment ID in a
subsequent Scan operation.
The value for Segment must be greater than or equal to 0, and less than
the value provided for TotalSegments .
If you specify Segment , you must also specify TotalSegments .
:type projection_expression: string
:param projection_expression: A string that identifies one or more
attributes to retrieve from the table. These attributes can include
scalars, sets, or elements of a JSON document. The attributes in
the expression must be separated by commas.
If no attribute names are specified, then all attributes will be
returned. If any of the requested attributes are not found, they
will not appear in the result.
For more information on projection expressions, go to `Accessing Item
Attributes`_ in the Amazon DynamoDB Developer Guide .
:type filter_expression: string
:param filter_expression: A condition that evaluates the scan results
and returns only the desired values.
The condition you specify is applied to the items scanned; any items
that do not match the expression are not returned.
: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 scan(self, table_name, attributes_to_get=None, limit=None, select=None, scan_filter=None, conditional_operator=None, exclusive_start_key=None, return_consumed_capacity=None, total_segments=None, segment=None, projection_expression=None, filter_expression=None, expression_attribute_names=None, expression_attribute_values=None):

    params = {'TableName': table_name}
    if (attributes_to_get is not None):
        params['AttributesToGet'] = attributes_to_get
    if (limit is not None):
        params['Limit'] = limit
    if (select is not None):
        params['Select'] = select
    if (scan_filter is not None):
        params['ScanFilter'] = scan_filter
    if (conditional_operator is not None):
        params['ConditionalOperator'] = conditional_operator
    if (exclusive_start_key is not None):
        params['ExclusiveStartKey'] = exclusive_start_key
    if (return_consumed_capacity is not None):
        params['ReturnConsumedCapacity'] = return_consumed_capacity
    if (total_segments is not None):
        params['TotalSegments'] = total_segments
    if (segment is not None):
        params['Segment'] = segment
    if (projection_expression is not None):
        params['ProjectionExpression'] = projection_expression
    if (filter_expression is not None):
        params['FilterExpression'] = filter_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='Scan', body=json.dumps(params))
