The sum of prime progression (Parallel)

sump.py

from multiprocessing import Pool
import time

def isPrime(n):
    if n < 2:
        return 0
    if n == 2:
        return n
    if n % 2 == 0:
        return 0
    i = 3
    while i * i <= n:
        if n % i == 0:
            return 0
        i += 2
    return n
#http://d.hatena.ne.jp/hagaeru3sei/20081029

def main():
    l = []
    ans = 0
    p = Pool(4)
    print sum(p.map(isPrime, range(2000000)))

if __name__ == '__main__':
    s = time.time()
    main()
    print 'time: %f' % (time.time() - s)