extre.py

# Experimental extensions to Python's re module.

import re

def int_class_expansion(match):
    return "(%s)" % \
        ('|'.join(reversed( [str(x) for x \
                             in xrange(int(match.group(1)),
                                       int(match.group(2))+ 1)] )))
int_class_rule = ( r"\[(\d+)\.\.(\d+)\]", int_class_expansion)

rules = [int_class_rule,]

def expand(pattern):
    result = pattern
    for rule in rules:
        match = re.search(rule[0], result)
        while match:
            result = result[:match.start()] + \
                     rule[1](match) + \
                     result[match.end():]
            match = re.search(rule[0], result)
    return result

def match(pattern, string, flags=0):
    return re.match(expand(pattern), string, flags)

def search(pattern, string, flags=0):
    return re.search(expand(pattern), string, flags)

#

I re-read Staffan's post and realized that he actually specifies that it should be greedy so my example above is clearly wrong. I've updated the code to make it behave as it should:

m = extre.match(r'([0..255].){3}[0..255]', '123.125.126.107')
m.group() '123.125.126.107'