Problems with regexps

[Ben Finney]

On Fri, 07 Nov 2003 23:00:34 GMT, Kirk Strauser wrote:
>     sample = 'FOO= BAR'
>
>     if re.search(r'[^=]\s+BAR', sample):
>         print 'Match 1.'
>
>     if re.search(r'[^=]\s*BAR', sample):
>         print 'Match 2.'
>
> When run, it produces "Match 2.".  Why?  I want to match:
>
>    1) Anything but '=', followed by
>    2) Zero or more spaces, followed by
>    3) 'BAR'

To understand the answer, you must understand the question.

If you inspect the MatchObject returned from re.search(), you'll learn
more about what's going on:

    >>> import re
    >>> sample = 'FOO= BAR'
    >>> match = re.search( r'[^=]\s+BAR', sample )
    >>> match

The first match returns the None object.

    >>> match = re.search( r'[^=]\s*BAR', sample )
    >>> match
    <_sre.SRE_Match object at 0x4021b090>

The second match returns a Match object; let's see what it matched.

    >>> match.group(0)
    ' BAR'
    >>>

The matching string contains the space ("Anything but '='"), followed by
nothing ("Zero or more spaces"), followed by BAR.  Exactly what you
asked for.

-- 
 \       "It is seldom that liberty of any kind is lost all at once."  |
  `\                                                     -- David Hume |
_o__)                                                                  |
Ben Finney <http://bignose.squidly.org/>