sieve prime example

prime.py

import math
import argparse

argument_parser = argparse.ArgumentParser()
argument_parser.add_argument("--n", type=int, required=True)
args = argument_parser.parse_args()


def is_prime(n):
    if n == 1:
        return False
    for i in range(2, int(math.sqrt(n)) + 1):
        if n % i == 0:
            return False
    return True

# excluding n


def primes_upto(n):
    marked = [True] * (n - 1)
    marked[0] = False
    marked[1] = False
    # print(marked)

    for i in range(2, n):
        status = is_prime(i)
        if status:
            print(f"Marking composites for {i}......")
            for j in range(i + 1, len(marked)):
                # if it's a multiple
                if j % i == 0:
                    marked[j] = False

    # find the primes
    primes = []
    for i in range(len(marked)):
        if marked[i]:
            primes.append(i)
    # return
    return primes


if __name__ == "__main__":
    primes = primes_upto(args.n)