regexps: testing and creating MatchObjects in one fell swoop

[Dan Schmidt]

I'm fond of the perl idiom

  if (/(\d+)\s+(\d+)/) {
    ($num1, $num2) = ($1, $2);
  }

(Yep, I know I could compress this even further if I wanted to.)

In Python, it seems I have to do the following:

  match = re.search (r"(\d+)\s+(\d+)", line)
  if match:
      (num1, num2) = match.groups()

I'd love to be able to write something like (and I know I can't):

  if (match = re.search (r"(\d+)\s+(\d+)", line)):
      (num1, num2) = match.groups()

This isn't a huge pain in the simple case, but it quickly becomes
annoying when I want to do the equivalent of

  if (/(\d+)\s+(\d+)/) {
    ($num1, $num2) = ($1, $2);
  } elsif (/(\w+)\s+(\w+)/) {
    ($word1, $word2) = ($1, $2):
  } # etc.

as the two-part test in Python doesn't lend itself easily to a long
if/elif/elif chain.

I've "solved" the problem locally by using the following helper
function:

  # research (regexp, string) is the same as regexp.search (string),
  # but saves off the match results into 'rematch', so we can test for
  # a regexp in an if statement and use the results immediately.
  rematch = None
  def research (regexp, string):
      global rematch
      rematch = regexp.search (string)
      return (rematch != None)

So that I can write:

  if research (r"(\d+)\s+(\d+)", line):
      (num1, num2) = rematch.groups()
  elif research (r"(\w+)\s+(\w+)", line):
      (word1, word2) = rematch.groups()
  # etc.

I suppose I can even inject research into the re module, and inject a
similar method into regular expression objects. etc, to make it nicer.

Is there a cleaner, or more approved, way, to accomplish this task?
If not, does it make any sense to have a re.last_match object that
automatically contains the last match, allowing, for example:

  if re.search (r"(\d+)\s+(\d+)", line):
      (num1, num2) = re.last_match.groups()

Or is that too side-effecty and non-Pythonic?

-- 
                 Dan Schmidt | http://www.dfan.org
Honest Bob CD now available! | http://www.dfan.org/honestbob/cd.html