Removing from the beginning of an array (list) requires moving all of the items after it down. That means that removing every element from a list in this way starting from the front is an O(n^2) operation.
You can do this much more efficiently with sets:
def primes_sieve(limit): limitn = limit+1 not_prime = set() primes = [] for i in range(2, limitn): if i in not_prime: continue for f in range(i*2, limitn, i): not_prime.add(f) primes.append(i) return primesprint primes_sieve(1000000)... or alternatively, avoid having to rearrange the list:
def primes_sieve(limit): limitn = limit+1 not_prime = [False] * limitn primes = [] for i in range(2, limitn): if not_prime[i]: continue for f in xrange(i*2, limitn, i): not_prime[f] = True primes.append(i) return primes