Add functools.CmpToKey()
diff --git a/Doc/library/functools.rst b/Doc/library/functools.rst
index 6dc9f0a..3337ead 100644
--- a/Doc/library/functools.rst
+++ b/Doc/library/functools.rst
@@ -17,6 +17,28 @@
The :mod:`functools` module defines the following functions:
+.. function:: CmpToKey(func)
+
+ Transform an old-style comparison function to a key-function. Used with
+ tools that accept key functions (such as :func:`sorted`, :func:`min`,
+ :func:`max`, :func:`heapq.nlargest`, :func:`heapq.nsmallest`,
+ :func:`itertools.groupby`).
+ This function is primarily used as a transition tool for programs
+ being converted to Py3.x where comparison functions are no longer
+ supported.
+
+ A compare function is any callable that accept two arguments, compares
+ them, and returns a negative number for less-than, zero for equality,
+ or a positive number for greater-than. A key function is a callable
+ that accepts one argument and returns another value that indicates
+ the position in the desired collation sequence.
+
+ Example::
+
+ sorted(iterable, key=CmpToKey(locale.strcoll)) # locale-aware sort order
+
+ .. versionadded:: 2.7
+
.. function:: total_ordering(cls)
Given a class defining one or more rich comparison ordering methods, this