Proof read/editing of abc. Added table of collections.Hashable etc. to
collections with some brief notes.
diff --git a/Doc/library/collections.rst b/Doc/library/collections.rst
index 50ddc0f..fe57f12 100644
--- a/Doc/library/collections.rst
+++ b/Doc/library/collections.rst
@@ -19,6 +19,55 @@
Future editions of the standard library may include balanced trees and
ordered dictionaries.
+In addition to containers, the collections module provides some ABCs
+(abstract base classes) that can be used to test whether
+a class provides a particular interface, for example, is it hashable or
+a mapping. The ABCs provided include those in the following table:
+
+===================================== ========================================
+ABC Notes
+===================================== ========================================
+:class:`collections.Container` Defines ``__contains__()``
+:class:`collections.Hashable` Defines ``__hash__()``
+:class:`collections.Iterable` Defines ``__iter__()``
+:class:`collections.Iterator` Derived from :class:`Iterable` and in
+ addition defines ``__next__()``
+:class:`collections.Mapping` Derived from :class:`Container`,
+ :class:`Iterable`,
+ and :class:`Sized`, and in addition
+ defines ``__getitem__()``, ``get()``,
+ ``__contains__()``, ``__len__()``,
+ ``__iter__()``, ``keys()``,
+ ``items()``, and ``values()``
+:class:`collections.MutableMapping` Derived from :class:`Mapping`
+:class:`collections.MutableSequence` Derived from :class:`Sequence`
+:class:`collections.MutableSet` Derived from :class:`Set` and in
+ addition defines ``add()``,
+ ``clear()``, ``discard()``, ``pop()``,
+ and ``toggle()``
+:class:`collections.Sequence` Derived from :class:`Container`,
+ :class:`Iterable`, and :class:`Sized`,
+ and in addition defines
+ ``__getitem__()``
+:class:`collections.Set` Derived from :class:`Container`, :class:`Iterable`, and :class:`Sized`
+:class:`collections.Sized` Defines ``__len__()``
+===================================== ========================================
+
+.. XXX Have not included them all and the notes are imcomplete
+.. Deliberately did one row wide to get a neater output
+
+These ABCs allow us to ask classes or instances if they provide
+particular functionality, for example::
+
+ from collections import Sized
+
+ size = None
+ if isinstance(myvar, Sized):
+ size = len(myvar)
+
+(For more about ABCs, see the :mod:`abc` module and :pep:`3119`.)
+
+
.. _deque-objects: