check prime

isprime.py

#! /usr/bin/python
 
from sys import argv
from math import sqrt
 
def is_prime(num):
    s = sqrt(num)
    step = 4
    if num <= 3:
        return True
    if num % 2 == 0 or num % 3 == 0:
        return False
    i = 5
    while i <= s:
        if num % i == 0:
            break
        step ^= 6
        i += step
    return i > s
 
a = int(argv[1])
 
print(is_prime(a))