Given a simplified regex, output all (possibly infinitely many) strings that it fully matches.

regex__match_generator.py

import string

alphanumerics = string.ascii_letters + string.digits
inf = float("inf")

def parse(regex):
    segments = []
    regex += " "
    for i, char in enumerate(regex):
        if char in alphanumerics:
            repetition_operator = regex[i+1] if regex[i+1] not in alphanumerics else " "
            lower_bound = 0 if repetition_operator in "*?" else 1
            upper_bound = inf if repetition_operator in "*+" else 1
            segments.append((char, lower_bound, upper_bound))
        else:
            continue
    return segments

def generate(regex_segments, length):
    char, lower, upper = regex_segments[0]
    if len(regex_segments) == 1:
        if lower <= length <= upper:
            yield char * length
    else:
        for first_count in range(length + 1):
            if lower <= first_count <= upper:
                for remainder in generate(regex_segments[1:], length - first_count):
                    yield char * first_count + remainder

def generate_all(regex_segments):
    length = 0
    while True:
        for result in generate(regex_segments, length):
            yield result
        length += 1


if __name__ == "__main__":
    test = parse("ab?c+d*")
    print(test)
    for match in generate_all(test):
        print(match)