Number modifier

modify_number.py

# -*- coding: utf-8 -*-

def get_number():
    return input('Введите число: ')


def to_int_or_none(number):
    try:
        return int(number)
    except ValueError:
        return None


def modify_number(number):
    if number % 2:
        return number * 3 + 1

    return number // 2


def get_modified_number(number):
    if number == 'cancel':
        return 'Bye!'

    number = to_int_or_none(number)

    if number is None:
        print('Не удалось преобразовать введенный текст в число.')

        number = get_number()
        modified_number = get_modified_number(number)

        return modified_number

    return modify_number(number)


if __name__ == '__main__':
    number = get_number()
    modified_number = get_modified_number(number)