Simple piface program to toggle outputs and keep state over restart

gistfile1.py

#!/usr/bin/env python

import os, time, pickle, pifaceio

filename = os.path.join(os.path.expanduser('~'), '.' +
        os.path.basename(__file__) + '.init')

pf = pifaceio.PiFace()

# Read stored last states
try:
    with open(filename, 'rb') as f:
        last_in, last_out = pickle.load(f)
except:
    last_in, last_out = 0, 0

pf.write(last_out)
print 'Wrote initial outputs 0x%02x' % last_out

# Read inputs and write changed outputs
while True:
    now_in = pf.read()

    new_in = now_in & (now_in ^ last_in)
    last_in = now_in
    new_out = (last_out & ~new_in) | ((last_out ^ new_in) & new_in)

    if new_out != last_out:
        last_out = new_out
        pf.write(new_out)
        print 'Wrote outputs 0x%02x' % new_out

        with open(filename, 'wb') as f:
            pickle.dump((last_in, last_out), f)

    time.sleep(.1)

where do i have to put this code in order for it to start with startup?