Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.python > #98198

Re: Regular expressions

Path csiph.com!fu-berlin.de!uni-berlin.de!not-for-mail
From Michael Torrie <torriem@gmail.com>
Newsgroups comp.lang.python
Subject Re: Regular expressions
Date Tue, 03 Nov 2015 19:04:23 -0700
Lines 37
Message-ID <mailman.0.1446602668.16136.python-list@python.org> (permalink)
References <662g3blobme52hfoududj27err185v2npm@4ax.com> <mailman.0.1446519578.8789.python-list@python.org> <hp9g3b9hsn06edb0po8bduegjqkmpo4p8n@4ax.com> <mailman.3.1446523111.8789.python-list@python.org> <d39290cf-cb26-470f-a987-2f71e3860f97@googlegroups.com> <mailman.5.1446525488.8789.python-list@python.org> <bb15756d-7181-421d-835e-b2fbfc1c1774@googlegroups.com>
Mime-Version 1.0
Content-Type text/plain; charset=windows-1252
Content-Transfer-Encoding 7bit
X-Trace news.uni-berlin.de f8irQnrTyMquyAUZjDQn7QQzP0gBILVftPE2YR/XddOA==
Return-Path <torriem+gmail@torriefamily.org>
X-Original-To python-list@python.org
Delivered-To python-list@mail.python.org
X-Spam-Status OK 0.000
X-Spam-Evidence '*H*': 1.00; '*S*': 0.00; 'patterns': 0.04; 'resulting': 0.04; 'expressions': 0.07; 'finite': 0.09; 'grep': 0.09; 'methods,': 0.09; 'patterns,': 0.09; 'res': 0.09; 'unexpected': 0.09; 'python': 0.10; 'index': 0.13; 'explicitly': 0.15; 'languages,': 0.15; 'cleanly': 0.16; 'describing': 0.16; 'expressions,': 0.16; 'from:addr:torriem': 0.16; 'from:name:michael torrie': 0.16; 'maintainable': 0.16; 'received:io': 0.16; 'received:psf.io': 0.16; 'regex,': 0.16; 'subject:Regular': 0.16; 'subject:expressions': 0.16; 'terse': 0.16; 'why,': 0.16; 'wrote:': 0.16; 'string': 0.17; 'say,': 0.18; 'programmer': 0.18; 'input': 0.18; 'language': 0.19; 'c++,': 0.22; 'programming': 0.22; 'code.': 0.23; 'bit': 0.23; 'ease': 0.23; 'header:In-Reply-To:1': 0.24; "i've": 0.25; 'header:User-Agent:1': 0.26; 'earlier': 0.27; 'supported': 0.27; 'not.': 0.27; 'regular': 0.29; 'etc).': 0.29; 'certainly': 0.30; 'query': 0.30; 'relative': 0.30; 'operations': 0.31; 'probably': 0.31; 'maybe': 0.33; 'class': 0.33; 'accessible': 0.33; 'message-id:@gmail.com': 0.34; 'know.': 0.34; 'except': 0.34; 'clear': 0.35; 'library.': 0.35; 'requiring': 0.35; 'but': 0.36; 'there': 0.36; '(and': 0.36; 'mode': 0.36; 'projects.': 0.36; "wasn't": 0.36; 'to:addr:python- list': 0.36; 'pm,': 0.36; 'subject:: ': 0.37; 'really': 0.37; 'received:org': 0.37; 'beyond': 0.37; 'things': 0.38; 'itself': 0.38; 'means': 0.39; "didn't": 0.39; 'received:192': 0.39; 'to:addr:python.org': 0.40; 'still': 0.40; 'skip:u 10': 0.61; 'default': 0.61; 'charset:windows-1252': 0.62; 'needing': 0.63; 'more': 0.63; 'more.': 0.63; 'developed': 0.66; 'python-list': 0.66; 'fact,': 0.67; 'college': 0.67; 'detecting': 0.84; 'pain': 0.84; 'maybe,': 0.91
X-Virus-Scanned amavisd-new at torriefamily.org
User-Agent Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0
In-Reply-To <bb15756d-7181-421d-835e-b2fbfc1c1774@googlegroups.com>
X-BeenThere python-list@python.org
X-Mailman-Version 2.1.20+
Precedence list
List-Id General discussion list for the Python programming language <python-list.python.org>
List-Unsubscribe <https://mail.python.org/mailman/options/python-list>, <mailto:python-list-request@python.org?subject=unsubscribe>
List-Archive <http://mail.python.org/pipermail/python-list/>
List-Post <mailto:python-list@python.org>
List-Help <mailto:python-list-request@python.org?subject=help>
List-Subscribe <https://mail.python.org/mailman/listinfo/python-list>, <mailto:python-list-request@python.org?subject=subscribe>
Xref csiph.com comp.lang.python:98198

Show key headers only | View raw

On 11/03/2015 05:33 PM, rurpy--- via Python-list wrote:
> I consider regexs more fundemental.  One need not even be a programmer
> to use them: consider grep, sed, a zillion editors, database query 
> languages, etc.

Grep can use regular expressions (and I do so with it regularly), but
it's default mode is certainly not regular expressions, and it is still
very powerful.  I've never used regular expressions in a database query
language; until this moment I didn't know any supported such things in
their queries.  Good to know.  How you would index for regular
expressions in queries I don't know.

> When there is a mini-language explicitly developed for describing
> string patterns, why, except is very simple cases, would one not
> take advantage of it?  

Mainly because the programming language itself often can do it just as
cleanly and just as fast (slicing, string methods, etc).  I certainly
programmed for many years without needing regular expressions in my
small projects.  In fact, REs are a bit of a pain to use in, say, C or
C++, requiring a library.  With Python they are much more readily
accessible so I use them much more.

But honestly it wasn't until college when I learned about finite state
automata that I really grasped what regular expressions were and how to
use them.

> Beyond trivial operations a regex, although
> terse (overly perhaps), is still likely to be more understandable 
> more maintainable than bunch of ad-hoc code.  And the relative ease 
> of expressing complex patterns means one is more likely to create
> more specific patterns, resulting in detecting unexpected input 
> earlier than with ad-hoc code. 

Maybe, maybe not.  Using Python string class methods is probably more
clear when such methods are sufficient.

Back to comp.lang.python | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Regular expressions Seymore4Head <Seymore4Head@Hotmail.invalid> - 2015-11-02 20:09 -0500
  Re: Regular expressions MRAB <python@mrabarnett.plus.com> - 2015-11-03 01:19 +0000
    Re: Regular expressions Seymore4Head <Seymore4Head@Hotmail.invalid> - 2015-11-02 22:17 -0500
  Re: Regular expressions Tim Chase <python.list@tim.thechases.com> - 2015-11-02 20:42 -0600
    Re: Regular expressions Seymore4Head <Seymore4Head@Hotmail.invalid> - 2015-11-02 22:17 -0500
      Re: Regular expressions Joel Goldstick <joel.goldstick@gmail.com> - 2015-11-02 22:58 -0500
        Re: Regular expressions rurpy@yahoo.com - 2015-11-02 20:23 -0800
          Re: Regular expressions Michael Torrie <torriem@gmail.com> - 2015-11-02 21:38 -0700
            Re: Regular expressions rurpy@yahoo.com - 2015-11-03 16:33 -0800
              Re: Regular expressions Michael Torrie <torriem@gmail.com> - 2015-11-03 19:04 -0700
                Re: Regular expressions Dan Sommers <dan@tombstonezero.net> - 2015-11-04 02:55 +0000
                Re: Regular expressions Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-11-04 14:23 +1100
                Re: Regular expressions Michael Torrie <torriem@gmail.com> - 2015-11-03 20:47 -0700
                Re: Regular expressions Grant Edwards <invalid@invalid.invalid> - 2015-11-04 13:27 +0000
                Re: Regular expressions Nobody <nobody@nowhere.invalid> - 2015-11-04 05:05 +0000
                Re: Regular expressions Peter Otten <__peter__@web.de> - 2015-11-04 09:57 +0100
                Re: Regular expressions Steven D'Aprano <steve@pearwood.info> - 2015-11-05 13:28 +1100
                Re: Regular expressions Tim Chase <python.list@tim.thechases.com> - 2015-11-04 20:48 -0600
                Re: Regular expressions Ben Finney <ben+python@benfinney.id.au> - 2015-11-05 14:03 +1100
                Re: Regular expressions Peter Otten <__peter__@web.de> - 2015-11-05 09:33 +0100
                Re: Regular expressions Steven D'Aprano <steve@pearwood.info> - 2015-11-05 23:05 +1100
                Re: Regular expressions Tim Chase <python.list@tim.thechases.com> - 2015-11-05 08:00 -0600
                Re: Regular expressions Albert van der Horst <albert@spenarnc.xs4all.nl> - 2015-11-05 13:39 +0000
                Re: Regular expressions Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2015-11-04 08:00 -0500
                Re: Regular expressions Michael Torrie <torriem@gmail.com> - 2015-11-04 08:13 -0700
                Re: Regular expressions Seymore4Head <Seymore4Head@Hotmail.invalid> - 2015-11-04 18:00 -0500
                Re: Regular expressions rurpy@yahoo.com - 2015-11-04 16:24 -0800
                Re: Regular expressions Steven D'Aprano <steve@pearwood.info> - 2015-11-05 13:24 +1100
                Re: Regular expressions rurpy@yahoo.com - 2015-11-04 21:59 -0800
                Re: Regular expressions Christian Gollwitzer <auriocus@gmx.de> - 2015-11-05 09:18 +0100
                Re: Regular expressions rurpy@yahoo.com - 2015-11-06 11:52 -0800
                Re: Regular expressions Christian Gollwitzer <auriocus@gmx.de> - 2015-11-06 21:36 +0100
                Re: Regular expressions Larry Martell <larry.martell@gmail.com> - 2015-11-06 15:42 -0500
                Re: Regular expressions Chris Angelico <rosuav@gmail.com> - 2015-11-05 11:34 +1100
                Re: Regular expressions rurpy@yahoo.com - 2015-11-04 22:27 -0800
                Re: Regular expressions Tim Chase <python.list@tim.thechases.com> - 2015-11-04 09:42 -0600
                Re: Regular expressions Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-11-05 20:55 +1300
                Re: Regular expressions Chris Angelico <rosuav@gmail.com> - 2015-11-05 19:06 +1100
                What does “grep” stand for? (was: Regular expressions) Ben Finney <ben+python@benfinney.id.au> - 2015-11-05 05:24 +1100
                Re: What does “grep” stand for? Christian Gollwitzer <auriocus@gmx.de> - 2015-11-04 20:38 +0100
                Re: What does “grep” stand for? Chris Angelico <rosuav@gmail.com> - 2015-11-05 11:42 +1100
                Re: What does “grep” stand for? Christian Gollwitzer <auriocus@gmx.de> - 2015-11-05 08:32 +0100
                Re: What does “grep” stand for? Chris Angelico <rosuav@gmail.com> - 2015-11-05 19:00 +1100
                Re: What does “grep” stand for? Random832 <random832@fastmail.com> - 2015-11-05 10:19 -0500
                Re: What does “grep” stand for? Grant Edwards <invalid@invalid.invalid> - 2015-11-05 18:29 +0000
                Re: What does “grep” stand for? Random832 <random832@fastmail.com> - 2015-11-05 14:56 -0500
                Re: What does “grep” stand for? Grant Edwards <invalid@invalid.invalid> - 2015-11-05 20:19 +0000
                Re: What does “grep” stand for? Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2015-11-05 20:18 -0500
                Re: What does “grep” stand for? Larry Hudson <orgnut@yahoo.com> - 2015-11-05 19:36 -0800
                Re: What does “grep” stand for? Dan Sommers <dan@tombstonezero.net> - 2015-11-06 05:31 +0000
                Re: What does “grep” stand for? William Ray Wing <wrw@mac.com> - 2015-11-06 08:25 -0500
                Re: What does “grep” stand for? Larry Hudson <orgnut@yahoo.com> - 2015-11-06 19:21 -0800
                Re: What does ???grep??? stand for? Grant Edwards <invalid@invalid.invalid> - 2015-11-06 14:15 +0000
                Re: What does ???grep??? stand for? Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2015-11-06 20:03 -0500
                Re: What does “grep” stand for? (was: Regular expressions) Tim Chase <python.list@tim.thechases.com> - 2015-11-04 13:05 -0600
                Re: Regular expressions Terry Reedy <tjreedy@udel.edu> - 2015-11-04 18:08 -0500
                Re: Regular expressions Seymore4Head <Seymore4Head@Hotmail.invalid> - 2015-11-04 18:29 -0500
              Re: Regular expressions Tim Chase <python.list@tim.thechases.com> - 2015-11-03 21:12 -0600
              Re: Regular expressions Chris Angelico <rosuav@gmail.com> - 2015-11-04 14:26 +1100
              Re: Regular expressions Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-11-04 14:48 +1100
                Re: Regular expressions Christian Gollwitzer <auriocus@gmx.de> - 2015-11-04 08:21 +0100
                Re: Regular expressions Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-11-04 19:47 +1100
                Re: Regular expressions rurpy@yahoo.com - 2015-11-04 06:43 -0800
                Re: Regular expressions rurpy@yahoo.com - 2015-11-04 06:38 -0800
                Re: Regular expressions Chris Angelico <rosuav@gmail.com> - 2015-11-05 01:52 +1100
                Re: Regular expressions rurpy@yahoo.com - 2015-11-04 16:13 -0800
                Re: Regular expressions Chris Angelico <rosuav@gmail.com> - 2015-11-05 11:33 +1100
                Re: Regular expressions rurpy@yahoo.com - 2015-11-04 21:42 -0800
                Re: Regular expressions Steven D'Aprano <steve@pearwood.info> - 2015-11-05 13:26 +1100
                Re: Regular expressions Ben Finney <ben+python@benfinney.id.au> - 2015-11-05 14:07 +1100
                Re: Regular expressions rurpy@yahoo.com - 2015-11-04 21:54 -0800
                Re: Regular expressions Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2015-11-05 10:14 +0100
                Re: Regular expressions Seymore4Head <Seymore4Head@Hotmail.invalid> - 2015-11-04 18:02 -0500
                Re: Regular expressions Steven D'Aprano <steve@pearwood.info> - 2015-11-05 11:54 +1100
                Re: Regular expressions Seymore4Head <Seymore4Head@Hotmail.invalid> - 2015-11-05 10:07 -0500
                Re: Regular expressions rurpy@yahoo.com - 2015-11-06 12:46 -0800
          Re: Regular expressions Steven D'Aprano <steve@pearwood.info> - 2015-11-03 18:15 +1100
            Re: Regular expressions Nick Sarbicki <nick.a.sarbicki@gmail.com> - 2015-11-03 08:43 +0000
            Re: Regular expressions rurpy@yahoo.com - 2015-11-03 16:22 -0800
      Re: Regular expressions Denis McMahon <denismfmcmahon@gmail.com> - 2015-11-03 12:38 +0000
      Re: Regular expressions Tim Chase <python.list@tim.thechases.com> - 2015-11-03 05:53 -0600
      Re: Regular expressions Joel Goldstick <joel.goldstick@gmail.com> - 2015-11-03 10:34 -0500
        Re: Regular expressions Seymore4Head <Seymore4Head@Hotmail.invalid> - 2015-11-03 11:10 -0500
          Re: Regular expressions Chris Angelico <rosuav@gmail.com> - 2015-11-04 03:20 +1100
            Re: Regular expressions Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-11-04 14:35 +1100
              Re: Regular expressions Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2015-11-04 12:41 +0100
    Re: Regular expressions Grant Edwards <invalid@invalid.invalid> - 2015-11-03 14:56 +0000
  Re: Regular expressions Michael Torrie <torriem@gmail.com> - 2015-11-02 20:51 -0700
    Re: Regular expressions rurpy@yahoo.com - 2015-11-02 20:23 -0800
      Re: Regular expressions Michael Torrie <torriem@gmail.com> - 2015-11-02 21:33 -0700
      Re: Regular expressions Robin Koch <robin.koch@t-online.de> - 2015-11-03 23:58 +0100
  Re: Regular expressions Peter Otten <__peter__@web.de> - 2015-11-03 10:25 +0100
  Re: Regular expressions Tim Chase <python.list@tim.thechases.com> - 2015-11-03 05:50 -0600
  Re: Regular expressions Peter Otten <__peter__@web.de> - 2015-11-03 15:00 +0100
    Re: Regular expressions Jussi Piitulainen <harvesting@makes.email.invalid> - 2015-11-03 17:12 +0200
      Irregular last line in a text file, was Re: Regular expressions Peter Otten <__peter__@web.de> - 2015-11-03 16:35 +0100
        Re: Irregular last line in a text file, was Re: Regular expressions Jussi Piitulainen <harvesting@makes.email.invalid> - 2015-11-03 18:42 +0200
      Re: Irregular last line in a text file, was Re: Regular expressions Tim Chase <python.list@tim.thechases.com> - 2015-11-03 10:56 -0600
        Re: Irregular last line in a text file, was Re: Regular expressions Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-11-04 14:39 +1100
          Re: Irregular last line in a text file, was Re: Regular expressions Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2015-11-04 10:07 +0000
          Re: Irregular last line in a text file, was Re: Regular expressions Tim Chase <python.list@tim.thechases.com> - 2015-11-04 09:33 -0600
      Re: Irregular last line in a text file, was Re: Regular expressions Peter Otten <__peter__@web.de> - 2015-11-03 18:44 +0100
      Re: Irregular last line in a text file, was Re: Regular expressions Ian Kelly <ian.g.kelly@gmail.com> - 2015-11-03 11:33 -0700
      Re: Irregular last line in a text file, was Re: Regular expressions Ian Kelly <ian.g.kelly@gmail.com> - 2015-11-03 11:39 -0700
      Re: Irregular last line in a text file, was Re: Regular expressions Tim Chase <python.list@tim.thechases.com> - 2015-11-03 13:45 -0600
        Re: Irregular last line in a text file, was Re: Regular expressions Grant Edwards <invalid@invalid.invalid> - 2015-11-03 22:15 +0000

csiph-web