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-rw-r--r--Doc/library/difflib.rst5
1 files changed, 5 insertions, 0 deletions
diff --git a/Doc/library/difflib.rst b/Doc/library/difflib.rst
index 433764c..c9d1eee 100644
--- a/Doc/library/difflib.rst
+++ b/Doc/library/difflib.rst
@@ -35,6 +35,11 @@ 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 whose duplicates 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
+ Python 3.2.
.. class:: Differ