From 0e31201848f45db86bea6bf5bd196e2db88fbfbe Mon Sep 17 00:00:00 2001 From: Raymond Hettinger Date: Tue, 10 Nov 2009 18:35:46 +0000 Subject: [PATCH] Show example of how to make a sorted dictionary --- Doc/library/collections.rst | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/Doc/library/collections.rst b/Doc/library/collections.rst index cd38956bffb..7770b8951bc 100644 --- a/Doc/library/collections.rst +++ b/Doc/library/collections.rst @@ -862,6 +862,28 @@ semantics pass-in keyword arguments using a regular unordered dictionary. `Equivalent OrderedDict recipe `_ 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. + :class:`UserDict` objects -------------------------