From: Georg Brandl <georg@python.org>
Date: Sat, 31 Jul 2010 08:00:13 +0000 (+0000)
Subject: #2986: document SequenceMatcher heuristic.
X-Git-Tag: v2.6.6rc1~100
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=6cb047b21c841450c1178720a1af5bebbbdbf21a;p=thirdparty%2FPython%2Fcpython.git

#2986: document SequenceMatcher heuristic.
---

diff --git a/Doc/library/difflib.rst b/Doc/library/difflib.rst
index d749e1458295..9cd76e36419c 100644
--- a/Doc/library/difflib.rst
+++ b/Doc/library/difflib.rst
@@ -37,6 +37,11 @@ diffs. For comparing directories and files, see also, the :mod:`filecmp` module.
    complicated way on how many elements the sequences have in common; best case
    time is linear.
 
+   **Heuristic:** To speed-up matching, items that appear more than 1% of the
+   time in sequences of at least 200 items are treated as junk.  This has the
+   unfortunate side-effect of giving bad results for sequences constructed from
+   a small set of items.  An option to turn off the heuristic will be added to a
+   future version.
 
 .. class:: Differ