[issue6931] dreadful performance in difflib: ndiff and HtmlDiff

[Charles-Francois Natali]

Charles-Francois Natali <neologix at free.fr> added the comment:

This is because difflib.ndiff (called by difflib.HtmlDiff.make_table), contrarily to difflib.unified_diff (and probably kdiff3), doesn't restrict itself to contiguous lines, and searches diff even inside lines, so the complexity is much worse (see how many times _fancy_replace and quick_ratio are being called).
It might be a good idea to allow the user to specify the type of diff needed (ndiff vs unified_diff).

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nosy: +neologix

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<http://bugs.python.org/issue6931>
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