From: Raymond Hettinger <python@rcn.com>
Date: Tue, 10 Nov 2009 19:35:55 +0000 (+0000)
Subject: Show example of how to make a sorted dictionary
X-Git-Tag: v2.7a1~126
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=610326d48ac112524ede8182f695fdf8115a0c92;p=thirdparty%2FPython%2Fcpython.git

Show example of how to make a sorted dictionary
---

diff --git a/Doc/library/collections.rst b/Doc/library/collections.rst
index c0d539f658a7..dc81c0ad1834 100644
--- a/Doc/library/collections.rst
+++ b/Doc/library/collections.rst
@@ -884,3 +884,25 @@ semantics pass-in keyword arguments using a regular unordered dictionary.
 
    `Equivalent OrderedDict recipe <http://code.activestate.com/recipes/576693/>`_
    that runs on Python 2.4 or later.
+
+Since an ordered dictionary remembers its insertion order, it can be used
+in conjuction with sorting to make a sorted dictionary::
+
+    >>> # regular unsorted dictionary
+    >>> d = {'banana': 3, 'apple':4, 'pear': 1, 'orange': 2}
+
+    >>> # dictionary sorted by key
+    >>> OrderedDict(sorted(d.items(), key=lambda t: t[0]))
+    OrderedDict([('apple', 4), ('banana', 3), ('orange', 2), ('pear', 1)])
+
+    >>> # dictionary sorted by value
+    >>> OrderedDict(sorted(d.items(), key=lambda t: t[1]))
+    OrderedDict([('pear', 1), ('orange', 2), ('banana', 3), ('apple', 4)])
+
+    >>> # dictionary sorted by length of the key string
+    >>> OrderedDict(sorted(d.items(), key=lambda t: len(t[0])))
+    OrderedDict([('pear', 1), ('apple', 4), ('orange', 2), ('banana', 3)])
+
+The new sorted dictionaries maintain their sort order when entries
+are deleted.  But when new keys are added, the keys are appended
+to the end and the sort is not maintained.