rsync backup

#!/usr/bin/env python

import os
import time

now = time.time()
prior_lock = '/home/.backup.lock'
pstamp = os.stat(prior_lock)[9]

if (now - pstamp) >= 604800:
    os.system("$(which rsync) -a --inplace /home/ root\@192.168.1.105:/home2/")
    os.system("$(which touch) " . pstamp)
    print "Backup complete."
else:
    print "Backup has already run."