Regexp : repeated group identification

[Vlastimil Brom]

2011/12/14 candide <candide at free.invalid>:
> Consider the following code
>
> # ----------------------------
> import re
>
> z=re.match('(Spam\d)+', 'Spam4Spam2Spam7Spam8')
> print z.group(0)
> print z.group(1)
> # ----------------------------
>
> outputting :
>
> ----------------------------
> Spam4Spam2Spam7Spam8
> Spam8
> ----------------------------
>
> The '(Spam\d)+' regexp is tested against 'Spam4Spam2Spam7Spam8' and the
> regexp matches the string.
>
> Group numbered one within the regex '(Spam\d)+' refers to Spam\d
>
> The fours substrings
>
> Spam4   Spam2   Spam7  and  Spam8
>
> match the group numbered 1.
>
> So I don't understand why z.group(1) gives the last substring (ie Spam8 as
> the output shows), why not an another one, Spam4 for example ?
> --
> http://mail.python.org/mailman/listinfo/python-list

Hi,
you may find a tiny notice in the re docs on this:
http://docs.python.org/library/re.html#re.MatchObject.group

"If a group is contained in a part of the pattern that matched
multiple times, the last match is returned."

If you need to work with the content captured in the repeated group,
you may check the new regex implementation:
http://pypi.python.org/pypi/regex

Which has a special "captures" method of the match object for this
(beyond many other improvements):

>>> import regex
>>> m=regex.match('(Spam\d)+', 'Spam4Spam2Spam7Spam8')
>>> m.captures(1)
['Spam4', 'Spam2', 'Spam7', 'Spam8']
>>>

hth,
  vbr