Get strings that look like a copy string in a given directory (recursively)

copy_strings.py

import os
import sys
import re

def list_files(directory, extension):
    result = []
    paths = [os.path.join(directory, name) for name in os.listdir(directory)]
    dirs = filter(os.path.isdir, paths)
    matches_ext = lambda path: os.path.splitext(path)[1] == extension
    files_matching_ext = filter(matches_ext, paths)
    return list(files_matching_ext) + [f for d in dirs for f in list_files(d, extension)]

REGEXP_NO_QUOTES = r'.*[a-zA-Z]+\s+[a-zA-Z]+.*';

def find_sentences(file_path):
    # Find copy strings with at least two words separated by space
    lines = []
    with open(file_path) as f:
        for number, line in enumerate(f):
            if (
                re.search("'{}'".format(REGEXP_NO_QUOTES), line) or
                re.search('"{}"'.format(REGEXP_NO_QUOTES), line)
            ):
                lines.append('{}: {}'.format(number, line.strip()))
    return lines

def main():
    path = (sys.argv[1:] or ['.'])[0]
    files = list_files(path, extension='.js')
    for file_path in files:
        sentences = find_sentences(file_path)
        if sentences:
            print()
            print(file_path)
            print('\n'.join(sentences))


if __name__ == '__main__':
    main()