New submission from Simon Descarpentries <silt...@acoeuro.com>: I, it's my 1st post here. I'm a French computer-science engineer with 10 years XP and manager at Acoeuro.com SSLL compagny. I suggested a better regexp integration on python-ideas a few months ago failing to convince getting things done.
Despite issue https://bugs.python.org/issue25391 closed in 2010, nothing seems visible on https://docs.python.org/3/library/difflib.html to help users anticipating that a string greatly matching at 199 characters length, won't at all at the 200th one. It's an inconsistent behavior that looks like a bug. #!/usr/bin/env python3 from difflib import SequenceMatcher a = 'ab'*400 b = 'ba'*400 for i in range(1, 400): diff_ratio = SequenceMatcher(None, a=a[:i], b=b[:i]).ratio() print('%3.i %.2f' % (i, diff_ratio), end=' ') not i % 10 and print('') EOF At 199c I have a 0.99 ratio, and 0.00 at 200c. The results are nearly the same with strings made of emails like in https://github.com/Siltaar/drop_alternatives especially comparing strings like : "performantsetdvelopperducontenusimilairepourvosprochainstweets.suivezn...@twitterbusinesspourdautresinfosetactus.testerlespublicitstwitterbusiness.twitter.com|@TwitterBusiness|Aide|SedsinscrireLemailsadresse@gggTwitter,Inc.MarketStreet,SuiteSanFrancisco,CA" "rducontenusimilairepourvosprochainsTweets.Suiveznous@TwitterBusinesspourprofiterdautresinfosetactus.TesterlesPublicitésTwitterbusiness.twitter.com@TwitterBusinessAideSedésinscrireTwitterInternationalCompanyOneCumberlandPlace,FenianStreetDublin,DAXIRELAND" Fortunately, I didn't experienced the problem using quick_ratio(). The documentation is not clear about ratio / quick_ratio / real_quick_ratio ; but looks like unstable. With in addition an inconsistent behavior it looks like worthing some fix. ---------- components: Library (Lib) messages: 305153 nosy: Siltaar priority: normal severity: normal status: open title: difflib SequenceMatcher ratio() still have unpredictable behavior type: behavior versions: Python 2.7, Python 3.5, Python 3.6 _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue31889> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
