collatz.py

import sys


def compute_collatz(number):
    if number % 2 == 0:
        return number / 2
    return (number * 3 + 1) / 2


def main():
    try:
        number = int(sys.argv[1])
    except:
        number = int(input("Pick a number: "))

    result = compute_collatz(number)
    counter = 1

    print(f"{counter} :> {result}")

    while result > 1:
        counter += 1
        result = compute_collatz(result)
        print(f"{counter} :> {result}")


if __name__ == "__main__":
    main()