a fast prime number generator

prime_numbers

def find_primes(n):

    is_prime = np.ones(n, dtype=bool)
    # remove 0 and 1 because we know they are not prime
    is_prime[0:2] = False
    # start from number 2
    for number in range(2 , n):
        if number**2 > n: break
        if is_prime[number]:
            is_prime[number*2::number] = False
    return np.where(is_prime)[0]

assert len(find_primes(100) == 25)
assert len(find_primes(1000) == 168)
assert len(find_primes(10000) == 1229)
assert len(find_primes(100000) == 9592)