sqlalchemy.orm.collections.MappedCollection

class documentation

class MappedCollection(dict):

A basic dictionary-based collection class.

Extends dict with the minimal bag semantics that collection classes require. set and remove are implemented in terms of a keying function: any callable that takes an object and returns an object for use as a dictionary key.

Method	`__init__`	Create a new collection with keying provided by keyfunc.
Method	`remove`	Remove an item by value, consulting the keyfunc for the key.
Method	`set`	Add an item by value, consulting the keyfunc for the key.
Instance Variable	`keyfunc`	Undocumented

def __init__(self, keyfunc):

Create a new collection with keying provided by keyfunc.

keyfunc may be any callable that takes an object and returns an object for use as a dictionary key.

The keyfunc will be called every time the ORM needs to add a member by value-only (such as when loading instances from the database) or remove a member. The usual cautions about dictionary keying apply- keyfunc(object) should return the same output for the life of the collection. Keying based on mutable properties can result in unreachable instances "lost" in the collection.

@collection.remover
@collection.internally_instrumented
def remove(self, value, _sa_initiator=None):

Remove an item by value, consulting the keyfunc for the key.

@collection.appender
@collection.internally_instrumented
def set(self, value, _sa_initiator=None):

Add an item by value, consulting the keyfunc for the key.

keyfunc =

Undocumented