change encoding with python

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

if __name__ == "__main__":
    base_dir = os.getcwd()
    filter = re.compile('\.h$|\.m$|\.cpp$|\.c$')
    for dirpath, dirnames, filenames in os.walk(base_dir):
        for filename in filenames:
            if filter.search(filename):
                p = os.path.join(dirpath, filename)
                action = 'nkf --utf8 %s > %s_' % (p, p)
                os.system(action)
                action = 'mv %s_ %s' % (p, p)
                os.system(action)