Generating a list of values a regex COULD match in Python

Question

I\'m trying to use a regex as an input, and from there generate all the possible values that the regex would match.

So, for example, if the regex is \"three-letter w

Answer 1

The set of matching strings is infinite if and only if there is a quantifier (+ or *) in your regexp. Your question doesn't seem to aim at those patterns. I rather believe that the product function from itertools might help here.

You might for instance introduce a special character indicating an arbitrary letter (e.g. an underscore), then build a pattern like this

patt = 'a_c'

and define your alphabet

youralphabet = 'abcde...'

and define a function generating all possible instances like this

def genInstances(patt):
    elems = [c if c != '_' else youralphabet for c in patt]
    return itertools.product(*elems)

You may then extend this approach to match real regexp by parsing your pattern for \d or [a-zA-Z] or whatever.