Prepend text to files matching pattern in current directory

prepend.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import sys
import os
from os.path import join

TEXT = """syntax = "proto2"\n"""

def main():
    for dirpath, _, files in os.walk("."):
        for f in files:
            if f.endswith(".proto"):
                with file(join(dirpath, f), 'r') as original: data = original.read()
                with file(join(dirpath, f), 'w') as modified: modified.write(TEXT + data)

if __name__ == '__main__':
    main()