Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!feeder.erje.net!eu.feeder.erje.net!newsfeed.xs4all.nl!newsfeed2a.news.xs4all.nl!xs4all!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail Return-Path: X-Original-To: python-list@python.org Delivered-To: python-list@mail.python.org X-Spam-Status: OK 0.003 X-Spam-Evidence: '*H*': 0.99; '*S*': 0.00; 'algorithm': 0.04; 'subject:Python': 0.06; 'expressions': 0.07; 'problem:': 0.07; 'string': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'spelled': 0.09; 'subject:module': 0.09; 'url:github': 0.09; 'translate': 0.10; 'python': 0.11; 'anyways,': 0.16; 'approaches.': 0.16; 'decision,': 0.16; 'expressions,': 0.16; 'kern': 0.16; 'received:80.91.229.3': 0.16; 'received:plane.gmane.org': 0.16; 'underlying': 0.16; 'wrote:': 0.18; 'library': 0.18; "python's": 0.19; 'this?': 0.23; 'header :User-Agent:1': 0.23; 'interpret': 0.24; 'subject:problem': 0.24; 'decide': 0.24; 'purposes': 0.26; 'least': 0.26; 'header:X -Complaints-To:1': 0.27; 'header:In-Reply-To:1': 0.27; 'matching': 0.30; 'robert': 0.30; 'url:wiki': 0.31; 'names.': 0.31; 'anyone': 0.31; 'this.': 0.32; 'probably': 0.32; 'supposed': 0.32; 'regular': 0.32; 'guess': 0.33; 'possible.': 0.35; 'there': 0.35; 'module.': 0.36; 'possible': 0.36; 'similar': 0.36; 'url:org': 0.36; 'should': 0.36; 'two': 0.37; 'implement': 0.38; 'to:addr :python-list': 0.38; 'rather': 0.38; 'little': 0.38; 'expect': 0.39; 'sure': 0.39; 'to:addr:python.org': 0.39; 'received:org': 0.40; 'even': 0.60; 'expression': 0.60; 'is.': 0.60; 'most': 0.60; 'new': 0.61; 'such': 0.63; 'decided': 0.64; 'our': 0.64; 'more': 0.64; 'different': 0.65; 'world': 0.66; 'believe': 0.68; 'yes': 0.68; 'stated': 0.69; 'differently:': 0.84; 'eco': 0.84; 'terrible': 0.84; 'hundred': 0.95 X-Injected-Via-Gmane: http://gmane.org/ To: python-list@python.org From: Robert Kern Subject: Re: Python's re module and genealogy problem Date: Wed, 11 Jun 2014 14:26:42 +0100 References: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Gmane-NNTP-Posting-Host: 213.1.240.226 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 In-Reply-To: X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: General discussion list for the Python programming language List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Newsgroups: comp.lang.python Message-ID: Lines: 46 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1402493220 news.xs4all.nl 2895 [2001:888:2000:d::a6]:60747 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:73170 On 2014-06-11 13:23, BrJohan wrote: > For some genealogical purposes I consider using Python's re module. > > Rather many names can be spelled in a number of similar ways, and in order to > match names even if they are spelled differently, I will build regular > expressions, each of which is supposed to match a number of similar names. > > I guess that there will be a few hundred such regular expressions covering most > popular names. > > Now, my problem: Is there a way to decide whether any two - or more - of those > regular expressions will match the same string? > > Or, stated a little differently: > > Can it, for a pair of regular expressions be decided whether at least one string > matching both of those regular expressions, can be constructed? > > If it is possible to make such a decision, then how? Anyone aware of an > algorithm for this? And if that isn't the best straight line for the old saying, I don't know what is. http://en.wikiquote.org/wiki/Jamie_Zawinski Anyways, to your new problem, yes it's possible. Search for "regular expression intersection" for possible approaches. You will probably have to translate the regular expression to a different formalism or at least a different library to implement this. Consider just listing out the different possibilities. All of your regexes should be "well-behaved" given the constraints of the domain (tightly bounded, at least). There are tools that help generate matching strings from a Python regex. This will help you QA your regexes, too, to be sure that they match what you expect them to and not match non-names. https://github.com/asciimoo/exrex -- Robert Kern "I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth." -- Umberto Eco