Jojo problem

jojo.py

# coding: utf-8

import sys

# For each integer 1..n, print "jojo" if it is a prime number, 
# else print the number.

def jojo_iter(num):
    if 1 <= num:
        yield 1
    
    sieve = [True] * (num + 1)
    for i in range(2, num + 1):
        yield "jojo" if sieve[i] else i
        for j in range(i, num + 1, i):
            sieve[j] = False
    
def main():
    num = int(sys.argv[1])
    for v in jojo_iter(num):
        print(v)
    
if __name__ == '__main__':
    main()