Re: Groups in regular expressions don't repeat as expected

Path	csiph.com!x330-a1.tempe.blueboxinc.net!usenet.pasdenom.info!aioe.org!news.swapon.de!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail
From	Neil Cerutti <neilc@norwich.edu>
Newsgroups	comp.lang.python
Subject	Re: Groups in regular expressions don't repeat as expected
Date	21 Apr 2011 13:16:36 GMT
Organization	Norwich University
Lines	43
Message-ID	<91ap1kF1pjU2@mid.individual.net> (permalink)
References	<4daf31e3$0$10596$742ec2ed@news.sonic.net> <918q69FjfgU2@mid.individual.net> <4daf4344$0$10519$742ec2ed@news.sonic.net>
Mime-Version	1.0
Content-Type	text/plain; charset=us-ascii
Content-Transfer-Encoding	7bit
X-Trace	individual.net LwC+lQP+rMz2MDcUZuSYPwEAclgqC7b3GQPS0Rc2BllGxdgRm4
Cancel-Lock	sha1:OszoiCCJcCg7EBHTODUEkISbJdE=
User-Agent	slrn/0.9.9p1/mm/ao (Win32)
Xref	x330-a1.tempe.blueboxinc.net comp.lang.python:3794

Show key headers only | View raw

On 2011-04-20, John Nagle <nagle@animats.com> wrote:
>      Findall does something a bit different. It returns a list of
> matches of the entire pattern, not repeats of groups within
> the pattern.
>
>      Consider a regular expression for matching domain names:
>
> >>> kre = re.compile(r'^([a-zA-Z0-9\-]+)(?:\.([a-zA-Z0-9\-]+))+$')
> >>> s = 'www.example.com'
> >>> ms = kre.match(s)
> >>> ms.groups()
> ('www', 'com')
> >>> msall = kre.findall(s)
> >>> msall
> [('www', 'com')]
>
> This is just a simple example.  But it illustrates an unnecessary
> limitation.  The matcher can do the repeated matching; you just can't
> get the results out.

Thanks for the further explantion.

Assuming a fake API that returned multiple group matches as a
tuple:

>>? print(re.match(r"^([a-z])+$", "abcdef").groups())
(('a', 'b', 'c', 'd', 'e', 'f'),)

I was thinking of applying findall something like this, but you
have to make multiple calls:

>>> m = re.match(r"^[a-z]+$", s)
>>> if m:
...   print(re.findall(r"[a-z]", m.group()))
...
['a', 'b', 'c', 'd', 'e', 'f']

I can see that getting really annoying. Is there a better way to
make multiple group matches accessible without adding a third
element type as a group element?

-- 
Neil Cerutti

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

Thread

Groups in regular expressions don't repeat as expected John Nagle <nagle@animats.com> - 2011-04-20 12:20 -0700
  Re: Groups in regular expressions don't repeat as expected Neil Cerutti <neilc@norwich.edu> - 2011-04-20 19:23 +0000
    Re: Groups in regular expressions don't repeat as expected John Nagle <nagle@animats.com> - 2011-04-20 13:34 -0700
      Re: Groups in regular expressions don't repeat as expected Neil Cerutti <neilc@norwich.edu> - 2011-04-21 13:16 +0000
        Re: Groups in regular expressions don't repeat as expected John Nagle <nagle@animats.com> - 2011-04-24 12:43 -0700
  Re: Groups in regular expressions don't repeat as expected MRAB <python@mrabarnett.plus.com> - 2011-04-20 21:03 +0100
  Re: Groups in regular expressions don't repeat as expected Vlastimil Brom <vlastimil.brom@gmail.com> - 2011-04-21 15:57 +0200
  Re: Groups in regular expressions don't repeat as expected Vlastimil Brom <vlastimil.brom@gmail.com> - 2011-04-21 20:36 +0200

csiph-web