From 86e9b6b16424ddbdd1a4a393cd295e95835b7ef2 Mon Sep 17 00:00:00 2001 From: Raymond Hettinger Date: Sun, 9 Nov 2014 17:20:56 -0800 Subject: [PATCH] Issue 22830: Clarify docs for functools.cmp_to_key(). --- Doc/library/functools.rst | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/Doc/library/functools.rst b/Doc/library/functools.rst index 7fd7d5826b6..d87fa58dd70 100644 --- a/Doc/library/functools.rst +++ b/Doc/library/functools.rst @@ -21,8 +21,8 @@ The :mod:`functools` module defines the following functions: .. function:: cmp_to_key(func) - Transform an old-style comparison function to a key function. Used with - tools that accept key functions (such as :func:`sorted`, :func:`min`, + Transform an old-style comparison function to a :term:`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 from Python 2 which supported the use of @@ -31,13 +31,14 @@ The :mod:`functools` module defines the following functions: A comparison 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 indicating the position in the desired - collation sequence. + argument and returns another value to be used as the sort key. Example:: sorted(iterable, key=cmp_to_key(locale.strcoll)) # locale-aware sort order + For sorting examples and a brief sorting tutorial, see :ref:`sortinghowto`. + .. versionadded:: 3.2