collections.abc — abstract base classes for containers

Purpose:Abstract base classes for container data types.

The collections.abc module contains abstract base classes that define the APIs for container data structures built into Python and provided by the collections module.

Abstract Base Classes
Class Base class(es) API Purpose
Container   Basic container features, such as the in operator.
Hashable   Adds support for providing a hash value for the container instance.
Iterable   Can create an iterator over the container contents.
Iterator Iterable Is an iterator over the container contents.
Generator Iterator Extends iterators with the generator protocol from PEP 342.
Sized   Adds methods for containers that know how big they are.
Callable   For containers that can be invoked as a function.
Sequence Sized, Iterable, Container Supports retrieving individual items, iterating, and changing the order of items.
MutableSequence Sequence Supports adding and removing items to an instance after it has been created.
ByteString Sequence Combined API of bytes and bytearray.
Set Sized, Iterable, Container Supports set operations such as intersection and union.
MutableSet Set Adds methods for manipulating the set contents after it is created.
Mapping Sized, Iterable, Container Defines the read-only API used by dict.
MutableMapping Mapping Defines the methods for manipulating the contents of a mapping after it is created.
MappingView Sized Defines the view API for accessing a mapping from an iterator.
ItemsView MappingView, Set Part of the view API.
KeysView MappingView, Set Part of the view API.
ValuesView MappingView Part of the view API.
Awaitable   API for objects that can be used in await expressions, such as coroutines.
Coroutine Awaitable API for classes that implement the coroutine protocol.
AsyncIterable   API for iterables compatible with async for, as defined in PEP 492.
AsyncIterator AsyncIterable API for asynchronous iterators.

Besides clearly defining the APIs for containers with different semantics, these abstract base classes can be used to test whether an object supports an API before invoking it using isinstance(). Some of the classes also provide implementations of methods, and they can be used as mix-ins to build up custom container types without implementing every method from scratch.