FairlyRandom clone

import argparse
import hashlib


def cli_args():
    parser = argparse.ArgumentParser()
    parser.add_argument('randomness')
    parser.add_argument('salt')
    parser.add_argument('min')
    parser.add_argument('max')
    return parser.parse_args()


def fairly_random(randomness, salt, min_num, max_num):
    num_retries = 0
    delta = max_num - min_num + 1
    evenly_divisible = ((2**64)//delta)*delta
    m = hashlib.sha256()
    m.update(randomness.encode('ascii'))
    m.update(('-'+salt).encode('ascii'))
    while True:
        m_int = int.from_bytes(m.digest()[:8], byteorder='big')
        if m_int < evenly_divisible:
            return (m_int % delta) + min_num
        m.update('-RETRY'.encode('ascii'))
        num_retries += 1


if __name__ == '__main__':
    _args = cli_args()
    print(fairly_random(_args.randomness, _args.salt, int(_args.min), int(_args.max)))