Path: csiph.com!x330-a1.tempe.blueboxinc.net!usenet.pasdenom.info!aioe.org!feeder.news-service.com!news2.euro.net!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 0.012 X-Spam-Evidence: '*H*': 0.98; '*S*': 0.00; 'continuation': 0.07; 'default:': 0.09; 'forum,': 0.09; 'collapsed': 0.16; 'constructed': 0.16; 'excluding': 0.16; 'explicitely': 0.16; 'expression,': 0.16; 'skip:r 50': 0.16; 'suggestions?': 0.16; 'cc:addr:python-list': 0.16; 'looked': 0.16; 'this:': 0.16; 'cc:no real name:2**0': 0.20; "haven't": 0.20; 'figure': 0.21; 'resolution': 0.21; 'subject:Question': 0.21; 'cc:2**0': 0.22; 'header:In-Reply-To:1': 0.22; '(or': 0.23; "i'm": 0.27; 'received:209.85.220': 0.27; 'problem': 0.28; 'url:mailman': 0.28; 'import': 0.28; 'message-id:@mail.gmail.com': 0.29; 'print': 0.29; 'cc:addr:python.org': 0.30; 'match': 0.30; '(maybe': 0.30; 'pattern': 0.30; "didn't": 0.31; 'hi,': 0.32; 'closing': 0.32; 'anyone': 0.32; "what's": 0.33; "can't": 0.33; 'url:listinfo': 0.33; "i've": 0.34; 'however,': 0.34; 'causing': 0.34; 'like:': 0.34; 'skip:" 20': 0.35; 'regular': 0.35; 'file': 0.36; 'url:python': 0.36; 'problems': 0.36; 'skip:" 10': 0.36; 'opposed': 0.37; 'but': 0.37; 'something': 0.37; 'two': 0.37; 'received:google.com': 0.38; 'url:org': 0.38; 'received:209.85': 0.38; 'non': 0.38; 'subject:: ': 0.39; 'correctly': 0.39; 'enough': 0.39; 'missing': 0.39; 'case': 0.39; "i'd": 0.40; 'third': 0.40; 'below': 0.62; 'believe': 0.65; 'demo': 0.80; 'skip:r 70': 0.84; 'greedy': 0.91 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; bh=Dtq9UaN7higFiIbFzQ/GL0K8o8n7mx1HVSEuE/gaPZg=; b=VVCuGC5gL0nU/AckEL3M0xhdu0gZjZMEK2trUkdQ4kcSOxM0N6Ow5MkYZ5JQaHKEa9 U02edOPAx/ymXLpaymDrjmJjc93uly5NheYNIbY1zJdW7J3YYVPwQQWFwsXIpaBMoQ8+ YpFSb1gbXCBKWkSTDXwI8EhSG2maA9pkmIz1M= MIME-Version: 1.0 In-Reply-To: <8537a563-69d7-4bce-b192-d9427aad0a7c@i14g2000yqg.googlegroups.com> References: <8537a563-69d7-4bce-b192-d9427aad0a7c@i14g2000yqg.googlegroups.com> Date: Tue, 11 Oct 2011 00:59:46 +0200 Subject: Re: Question: Optional Regular Expression Grouping From: Vlastimil Brom To: galyle Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Cc: python-list@python.org X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.12 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: 48 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1318287589 news.xs4all.nl 2514 [2001:888:2000:d::a6]:60690 X-Complaints-To: abuse@xs4all.nl Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:14419 2011/10/10 galyle : > HI, I've looked through this forum, but I haven't been able to find a > resolution to the problem I'm having (maybe I didn't look hard enough > -- I have to believe this has come up before). =A0The problem is this: > I have a file which has 0, 2, or 3 groups that I'd like to record; > however, in the case of 3 groups, the third group is correctly > captured, but the first two groups get collapsed into just one group. > I'm sure that I'm missing something in the way I've constructed my > regular expression, but I can't figure out what's wrong. =A0Does anyone > have any suggestions? > > The demo below showcases the problem I'm having: > > import re > > valid_line =3D re.compile('^\[(\S+)\]\[(\S+)\](?:\s+|\[(\S+)\])=3D|\s+[\d= \ > [\']+.*$') > line1 =3D "[field1][field2] =3D blarg" > line2 =3D " =A0 =A0'a continuation of blarg'" > line3 =3D "[field1][field2][field3] =3D blorg" > > m =3D valid_line.match(line1) > print 'Expected: ' + m.group(1) + ', ' + m.group(2) > m =3D valid_line.match(line2) > print 'Expected: ' + str(m.group(1)) > m =3D valid_line.match(line3) > print 'Uh-oh: ' + m.group(1) + ', ' + m.group(2) > -- > http://mail.python.org/mailman/listinfo/python-list > Hi, I believe, the space before =3D is causing problems (or the pattern missing= it); you also need non greedy quantifiers +? to match as little as possible as opposed to the greedy default: valid_line =3D re.compile('^\[(\S+?)\]\[(\S+?)\](?:\s+|\[(\S+)\])\s*=3D|\s+= [\d\[\']+.*$') or you can use word-patterns explicitely excluding the closing ], like: valid_line =3D re.compile('^\[([^\]]+)\]\[([^\]]+)\](?:\s+|\[([^\]]+)\])\s*= =3D|\s+[\d\[\']+.*$') hth vbr