import math
 
def is_prime(n):
    if n < 2: return False
    if n == 2: return True
    if n % 2 == 0: return False
    for i in range(3, int(n/2) + 1, 2):   # int(math.sqrt(num))
        if n % i == 0:
            return False
    return True
 
def sum_prime(num):
    if num < 2:
        return 0
    sum_p = 2
    prime_lis = []
    suspected = set(range(3, num + 1, 2))
    for i in range(3, int(math.sqrt(num)) + 1, 2):   
        if is_prime(i):
            prime_lis.append(i)
    for p in prime_lis:
        sum_p += p
        suspected.difference_update(set(range(p, num + 1, p)))
    return sum(suspected) + sum_p
 
print sum_prime(2000000)

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MjAwazogMC4wOXMgOC4zIE1CCjQwMGs6IDAuMTlzIDcuOCBNQiAgICAgKHRlc3RzIGRvbmUgd2l0aCBzcXJ0IG9uIGxpbmUgIzcsIHNvIG5vIGRpZmZlcmVuY2UhKQo4MDBrOiAwLjQ4cyA4LjkgTUIgICAKMm1sbjogMS4xNXMgOC4wIE1CICAgbl4wLjk1ICBuXjEuMSAgbl4xLjEgICAoZW1waXJpY2FsIG9yZGVycyBvZiBncm93dGggY29tcGF0aWJsZSB3aXRoIGBuIGxvZyhsb2cgbilgKQ==

200k: 0.09s 8.3 MB
400k: 0.19s 7.8 MB     (tests done with sqrt on line #7, so no difference!)
800k: 0.48s 8.9 MB   
2mln: 1.15s 8.0 MB   n^0.95  n^1.1  n^1.1   (empirical orders of growth compatible with `n log(log n)`)