Speed up this code?

[Gregory Petrosyan]

# Paul Rubin's version
gregory at home:~$ python -mtimeit "import test2" "test2.primes(1000)"
100 loops, best of 3: 14.3 msec per loop

# version from the Cookbook
gregory at home:~$ python -mtimeit "import test1" "test1.primes(1000)"
1000 loops, best of 3: 528 usec per loop