Rename filenames in directory structure based on their folder index

renamer.py

import os
import re

# file rename example:
#   sub-directory: "1. Introduction"
#           files: "1. foo", "2. bar", ... => "1.1 foo", "1.2 bar", ...

path = '.'
for root, dirs, files in os.walk(path):
    for file_name in files:
        file_path = os.path.join(root, file_name)
        print(file_path)
        index_regex = re.compile(r'\/(\d+)\.')
        if re.search(index_regex, file_path):
            file_index = re.search(index_regex, file_path).group(1)
            new_file_path = os.path.join(root, file_index + '.' + file_name)
            print(new_file_path)
            os.rename(file_path, new_file_path)
        print()