gistfile1.py

from itertools import ifilter
from itertools import islice


def sieve_worker(numbers, table):
    head = next(numbers)
    if head not in table:
        yield head
        table[head+head] = [head]
    else:
        primes = table[head]
        del table[head]
        for prime in primes:
            next_filter = head+prime
            if next_filter in table:
                table[next_filter].append(prime)
            else:
                table[next_filter] = [prime]
    for prime in sieve_worker(numbers, table):
        yield prime

def sieve(numbers):
    for prime in sieve_worker(numbers, {}):
        yield prime

for i in islice(sieve(itertools.count(2)), 50): 
    print i

# test