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Groups > comp.lang.python > #98140

Re: Regular expressions

From Nick Sarbicki <nick.a.sarbicki@gmail.com>
Newsgroups comp.lang.python
Subject Re: Regular expressions
Date 2015-11-03 08:43 +0000
Message-ID <mailman.9.1446540211.8789.python-list@python.org> (permalink)
References (1 earlier) <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> <56385efc$0$1598$c3e8da3$5496439d@news.astraweb.com>

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On Tue, Nov 3, 2015 at 7:15 AM, Steven D'Aprano <steve@pearwood.info> wrote:

> On Tue, 3 Nov 2015 03:23 pm, rurpy@yahoo.com wrote:
>
> > Regular expressions should be learned by every programmer or by anyone
> > who wants to use computers as a tool.  They are a fundamental part of
> > computer science and are used in all sorts of matching and searching
> > from compilers down to your work-a-day text editor.
>
> You are absolutely right.
>
> If only regular expressions weren't such an overly-terse, cryptic
> mini-language, with all but no debugging capabilities, they would be great.
>
> If only there wasn't an extensive culture of regular expression abuse
> within
> programming communities, they would be fine.
>
> All technologies are open to abuse. But we don't say:
>
>   Some people, when confronted with a problem, think "I know, I'll use
>   arithmetic." Now they have two problems.
>
> because abuse of arithmetic is rare. It's hard to misuse it, and while
> arithmetic can be complicated, it's rare for programmers to abuse it. But
> the same cannot be said for regexes -- they are regularly misused, abused,
> and down-right hard to use right even when you have a good reason for using
> them:
>
> http://www.thedailywtf.com/articles/Irregular_Expression
>
> http://blog.codinghorror.com/regex-use-vs-regex-abuse/
>
>
> http://psung.blogspot.com.au/2008/01/wonderful-abuse-of-regular-expressions.html
>
>
> If there is one person who has done more to create a regex culture, it is
> Larry Wall, inventor of Perl. Even Larry Wall says that regexes are
> overused and their syntax is harmful, and he has recreated them for Perl 6:
>
> http://www.perl.com/pub/2002/06/04/apo5.html
>
> Oh, and the icing on the cake, regexes can be a security vulnerability too:
>
>
> https://www.owasp.org/index.php/Regular_expression_Denial_of_Service_-_ReDoS
>
>
>
> --
> Steven
>
> --
> https://mail.python.org/mailman/listinfo/python-list
>


+1

I agree that regex is an entirely necessary part of a programmers toolkit,
but dear god some people need to be taught restraint. The majority of
people I talk about regex to have no idea when and where it shouldn't be
used.

As an example part of my job is bringing our legacy Python code into the
modern day, and one of the largest roadblocks is the amount of regex used.

Some is necessary.

Some can be replaced by an `if word in str` or something similarly basic.

Some spans hundreds of lines and causes acute alopecia.

Just yesterday I found a colleague trying to parse HTML with regex.

So yes, teach regex, but teach it after the basics, and please emphasise
when it is appropriate to use it.

Yes I am bitter.

- Nick.

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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

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