Backup and un-backup file in Python

bak.py

#! /usr/bin/env python

import sys
import os

if __name__ == '__main__':
    for f in sys.argv[1:]:
        os.system('mv -v %s %s.bak' % (f, f))

unbak.py

#! /usr/bin/env python

import sys
import os
import re

if __name__ == '__main__':
    if len(sys.argv) < 2:
        print "Please give bak files"
        sys.exit(1)

    bak_ext = re.compile(r"(?P<filename>.*)\.bak")
        
    for f in sys.argv[1:]:
        result = re.match(bak_ext, f)
        if result is None:
            print "Skip %s: not ends with .bak" % f
        else:
            os.system('mv -v %s %s' % (f, result.group('filename')))