[Tutor] Why doesn't this regex match???

Sheila King sheila@thinkspot.net
Fri, 08 Feb 2002 23:26:53 -0800

On Fri, 08 Feb 2002 21:30:15 -0800, Sheila King <sheila@thinkspot.net>
wrote about [Tutor] Why doesn't this regex match???:

> OK, I'm having some trouble with using the re module for regular
> expression matching. (I'm very new to using regular expressions, so I
> suppose I could be doing something really stupid?)

Despite Tim's excellent advice, to reconsider whether I really want to
use regular expressions, I persist at that task. (I've been programming
long enough to feel that I ought to have learned them by now. And I'd
like to start understanding them so when other people discuss them I
don't feel lost.)

So, I decided I could possibly solve my problem with the whole "word
boundary" thing (when my phrase-pattern doesn't begin and end in an
alphanumeric character) as follows:

Match on any of the following at the beginning of the phrase-pattern:

The beginning of the searched string
A word boundary
White space

and any of the following at the end of the phrase-pattern:

The end of the searched string
A word boundary
White space

Seems to me, that this should about cover things???

So I tried the following, with the dismal results shown. Now what am I
doing wrong? 

>>> searchstring = 'ADV: FREE FREE OFFERZ!!!!'
>>> word = 'adv:'
>>> p = re.compile(r'[\b\A\s]%s[\b\Z\s]' % word, re.I)
Traceback (most recent call last):
  File "<pyshell#45>", line 1, in ?
    p = re.compile(r'[\b\A\s]%s[\b\Z\s]' % word, re.I)
  File "E:\PYTHON\PYTHON22\lib\sre.py", line 178, in compile
    return _compile(pattern, flags)
  File "E:\PYTHON\PYTHON22\lib\sre.py", line 228, in _compile
    raise error, v # invalid expression
error: internal: unsupported set operator

Note: it doesn't matter whether I make it a raw string or not. Same
error both ways. Clearly something isn't right with the pattern I'm
trying to use.

Sheila King

"When introducing your puppy to an adult cat,
restrain the puppy, not the cat." -- Gwen Bailey,
_The Perfect Puppy: How to Raise a Well-behaved Dog_