From 6cb047b21c841450c1178720a1af5bebbbdbf21a Mon Sep 17 00:00:00 2001 From: Georg Brandl Date: Sat, 31 Jul 2010 08:00:13 +0000 Subject: [PATCH] #2986: document SequenceMatcher heuristic. --- Doc/library/difflib.rst | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/Doc/library/difflib.rst b/Doc/library/difflib.rst index d749e145829..9cd76e36419 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