primes.py

#!/usr/bin/env python

import sys

def primes(n):
	if n < 2:
		return []
	s = range(3, n+1, 2)
	mroot = n ** 0.5
	half = (n+1) / 2 - 1
	i = 0
	m = 3
	while m <= mroot:
		if s[i]:
			j = (m*m - 3) / 2
			s[j] = 0
			while j < half:
				s[j] = 0
				j += m
		i = i + 1
		m = 2*i + 3
	return [2] + [ x for x in s if x ]

if __name__ == '__main__':
	primes_list =  primes(int(sys.argv[1]))
	print len(primes_list), primes_list