Speed test!

primes.py

import timeit


setup = """
def primes(n):
    '''Get all primes up to n.'''
    if n < 2:
        return []
    nums = range(n)
    sieve = set(xrange(2, n))
    for num in nums[:int(n ** 0.5) + 1]:
        if num in sieve:
            sieve -= set(nums[num**2::num])
    return sieve
"""

setup2 = """
def primes(n):
    '''Get all primes up to n.'''
    n = int(n)
    if n < 2:
        return []
    sieve = range(n)
    sieve[1] = 0
    root = n ** 0.5
    index = 0
    while index <= root:
        if sieve[index]:
            i = index ** 2
            while i < n:
                sieve[i] = 0
                i += index
        index += 1
    return [x for x in sieve if x]
"""

print min(timeit.Timer('primes(2000)', setup=setup).repeat(7, 1000))
print min(timeit.Timer('primes(2000)', setup=setup2).repeat(7, 1000))
# 0.27396607399
# 0.482172966003