Python script to replace tabs with spaces recursively for all files matching a specified file mask regex, the number of spaces if configurable

tabs2spaces.py

#
# Usage:
#
# python tabs2spaces.py . 2 .*\.js$
#
import argparse
import os
import re

parser = argparse.ArgumentParser(description='Replace tabs with spaces.')
parser.add_argument('root_directory', type=str, default='.', nargs='?',
                   help='directory to run the script in')
parser.add_argument('spaces_for_tab', type=int, default=2, nargs='?',
                   help='number of spaces for one tab')
parser.add_argument('file_mask_regex', default=".*", nargs='?',
                   help='file name mask regex')

args = parser.parse_args()
file_mask_regex = re.compile(args.file_mask_regex)
replacement_spaces = ' ' * args.spaces_for_tab

print('Starting tab replacement. \
directory {0}, spaces number {1}, file mask {2}'.format(args.root_directory, args.spaces_for_tab, args.file_mask_regex))

found_files = []
for path, subdirs, files in os.walk(args.root_directory):
    for name in files:
        found_files.append(os.path.join(path, name));

matched_files = [name for name in found_files if file_mask_regex.match(name)]

for file_path in matched_files:
    file_contents = ''
    with open(file_path) as f:
        file_contents = f.read()

    file_contents = re.sub('\t', replacement_spaces, file_contents)

    print('Replacing tabs in {0}'.format(file_path))
    with open(file_path, "w") as f:
        f.write(file_contents)

print('Done')

Simply replace tabs with specified number of spaces is not perfectly equal to the effect of using spaces originally.
You may refer to my implementation: https://github.com/zchrissirhcz/smart_code_copier

@zchrissirhcz Link 404'd. Do you mind explaining how they're not perfectly equal?

@jcwii Sorry that I made my repo private since I thought my implementation is not very elegant(and using clang-format is an alternantive).. Now it is public again

My comment saying "not perfectly equal", an examle would demonstrate what that mean:

    std::cout   << "hello world" << endl;

In this example line, there are 4 spaces before std::cout, this is the same when specify tabsize=4. However, there are 3 spaces between std::cout and << when you type tab right after std::cout, instead of 4, thus replacing it with 4 spaces would make it not match the original meaning of table symbol.

@zchrissirhcz the explanation and efforts are both very kind of you. Thank you Zhuo Zhang.