from timeit import timeit
print '{:<12}\t{:.3}s'.format('str.zfill()', timeit("'6'.zfill(8)"))
print '{:<12}\t{:.3}s'.format('str.format()', timeit("'{0:08b}'.format(6)"))
print '{:<12}\t{:.3}s'.format('format()', timeit("format(6, '08b')"))