Just a simple tool to remap long regular patterns with shorter ones, useful for comparing two sets of data for equality

pattern_to_seq.py

import re
import sys
import string

def _get_fh(has_fname):
    if has_fname:
        return open(sys.argv[1])
    else:
        return sys.stdin


def _get_pattern(has_fname):
    pattern = sys.argv[2] if has_fname else sys.argv[1]
    return pattern


def run(input_handle, pattern, seq):
    substitutions = dict()

    for line in input_handle.readlines():
        match = re.search(pattern, line)
        if match:  # TODO: could be several patterns on same line
            match_string = match[0]

            if match_string in substitutions:
                repl = substitutions[match_string]
            else:
                substitutions[match_string] = next(seq)
                repl = substitutions[match_string]
            line = re.sub(pattern, repl, line)
        print(line.rstrip('\r\n'))


if len(sys.argv) < 2:
    print("Usage: pattern_to_seq [file] pattern")
    sys.exit(1)


def make_gen(max_numval):
    max_numgen_val = 2**32
    num_gen = iter(range(0, max_numgen_val))
    alpha_prefix_gen = iter(string.ascii_uppercase)
    pre_prefix = next(alpha_prefix_gen)

    while True:
        i = next(num_gen)

        if i and i % max_numval == 0 and pre_prefix != 'Z':
            pre_prefix = next(alpha_prefix_gen)
            num_gen = iter(range(0, max_numgen_val))
            i = next(num_gen)

        yield '{}{}'.format(pre_prefix, i)


if __name__ == '__main__':
    fname_present = len(sys.argv) == 3
    run(_get_fh(fname_present), _get_pattern(fname_present), make_gen(10000))