From 9b1e92f5a199acf20041372950b96e5896e1b634 Mon Sep 17 00:00:00 2001 From: Ezio Melotti Date: Tue, 28 Oct 2014 12:57:11 +0100 Subject: [PATCH] #22237: document that sorted() is guaranteed to be stable. Initial patch by Martin Panter. --- Doc/library/functions.rst | 5 +++++ Doc/library/heapq.rst | 4 +++- 2 files changed, 8 insertions(+), 1 deletion(-) diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst index 8b69b62aff5..3766d43da26 100644 --- a/Doc/library/functions.rst +++ b/Doc/library/functions.rst @@ -1286,6 +1286,11 @@ are always available. They are listed here in alphabetical order. Use :func:`functools.cmp_to_key` to convert an old-style *cmp* function to a *key* function. + The built-in :func:`sorted` function is guaranteed to be stable. A sort is + stable if it guarantees not to change the relative order of elements that + compare equal --- this is helpful for sorting in multiple passes (for + example, sort by department, then by salary grade). + For sorting examples and a brief sorting tutorial, see `Sorting HowTo `_\. diff --git a/Doc/library/heapq.rst b/Doc/library/heapq.rst index 4f1a682a875..6a6148025b5 100644 --- a/Doc/library/heapq.rst +++ b/Doc/library/heapq.rst @@ -123,7 +123,6 @@ pushing all values onto a heap and then popping off the smallest values one at a time:: >>> def heapsort(iterable): - ... 'Equivalent to sorted(iterable)' ... h = [] ... for value in iterable: ... heappush(h, value) @@ -132,6 +131,9 @@ time:: >>> heapsort([1, 3, 5, 7, 9, 2, 4, 6, 8, 0]) [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] +This is similar to ``sorted(iterable)``, but unlike :func:`sorted`, this +implementation is not stable. + Heap elements can be tuples. This is useful for assigning comparison values (such as task priorities) alongside the main record being tracked::