Path: csiph.com!fu-berlin.de!uni-berlin.de!not-for-mail From: Peter Otten <__peter__@web.de> Newsgroups: comp.lang.python Subject: Re: Regular expressions Date: Wed, 04 Nov 2015 09:57:02 +0100 Organization: None Lines: 52 Message-ID: References: <662g3blobme52hfoududj27err185v2npm@4ax.com> <56397a18$0$11094$c3e8da3@news.astraweb.com> <56397FC6.9040700@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7Bit X-Trace: news.uni-berlin.de iUY3vkBrsPdjph1WV/74agl9P9QBfmJg9KvJOg304kAA== Return-Path: X-Original-To: python-list@python.org Delivered-To: python-list@mail.python.org X-Spam-Status: OK 0.001 X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; '"""': 0.05; 'default.': 0.07; 'expressions': 0.07; 'grep': 0.09; 'indicates': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; '"grep': 0.16; '\\).': 0.16; 'egrep': 0.16; 'expressions.': 0.16; 'magic': 0.16; 'mistake.': 0.16; 'received:80.91.229.3': 0.16; 'received:dip0.t-ipconnect.de': 0.16; 'received:io': 0.16; 'received:plane.gmane.org': 0.16; 'received:psf.io': 0.16; 'received:t-ipconnect.de': 0.16; 'remembered': 0.16; 'say.': 0.16; 'subject:Regular': 0.16; 'subject:expressions': 0.16; "tim's": 0.16; 'wrote:': 0.16; '>>>': 0.20; 'versions': 0.20; 'matching': 0.23; 'tried': 0.24; "i've": 0.25; 'header:User-Agent:1': 0.26; 'example': 0.26; 'header:X-Complaints-To:1': 0.26; 'used,': 0.27; 'least': 0.27; 'gnu': 0.27; 'page.': 0.28; 'regular': 0.29; 'about.': 0.29; 'subset': 0.29; "i'm": 0.30; 'certainly': 0.30; 'another': 0.32; 'michael': 0.33; 'usually': 0.33; "d'aprano": 0.33; 'stands': 0.33; 'steven': 0.33; 'surprised': 0.33; 'something': 0.35; 'but': 0.36; 'instead': 0.36; 'there': 0.36; 'lines': 0.36; '(and': 0.36; 'basic': 0.36; 'mode': 0.36; 'to:addr :python-list': 0.36; 'pm,': 0.36; 'subject:: ': 0.37; 'received:org': 0.37; 'mean': 0.38; "didn't": 0.39; 'takes': 0.39; 'to:addr:python.org': 0.40; 'still': 0.40; 'received:de': 0.40; 'called': 0.40; 'default': 0.61; 'lose': 0.63; 'more': 0.63; 'times': 0.63; 'course.': 0.67; 'night': 0.67; 'talking': 0.67; 'special': 0.73; 'headed': 0.84 X-Injected-Via-Gmane: http://gmane.org/ X-Gmane-NNTP-Posting-Host: p57bd837e.dip0.t-ipconnect.de User-Agent: KNode/4.13.3 X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.20+ Precedence: list List-Id: General discussion list for the Python programming language List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Xref: csiph.com comp.lang.python:98215 Michael Torrie wrote: > On 11/03/2015 08:23 PM, Steven D'Aprano wrote: >>>> Grep can use regular expressions (and I do so with it regularly), but >>>> it's default mode is certainly not regular expressions ... >>> >>> Its very name indicates that its default mode most certainly is regular >>> expressions. >> >> I don't even know what grep stands for. >> >> But I think what Michael may mean is that if you "grep foo", no regex >> magic takes place since "foo" contains no metacharacters. > > More likely I just don't know what I'm talking about. I must have been > thinking about something else (shell globbing perhaps). > > Certainly most of the times I've seen grep used, it's to look for a word > with no special metacharacters, as you say. Still a valid RE of course. > But I have learned to night I don't need to resort to grep -e to use > regular expressions. At least with GNU grep, that's the default. Well, I didn't know that grep uses regular expressions by default. I tried Tim's example $ seq 5 | grep '1*' 1 2 3 4 5 $ which surprised me because I remembered that there usually weren't any matching lines when I invoked grep instead of egrep by mistake. So I tried another one $ seq 5 | grep '[1-3]+' $ and then headed for the man page. Apparently there is a subset called "basic regular expressions": """ Basic vs Extended Regular Expressions In basic regular expressions the meta-characters ?, +, {, |, (, and ) lose their special meaning; instead use the backslashed versions \?, \+, \{, \|, \(, and \). """