missing_number.py

def print_missing_number(nums):
    should_be = 0
    current = 0
    for i, n in enumerate(nums, 1):
        current += n
        should_be += i
    print(f"should_be: {should_be}, current: {current}")
    print(should_be - current)


def main():
    import random
    total_length = random.randint(2, 9)
    takeout = random.randint(0, total_length)
    nums = set(n for n in range(total_length))
    print(f"Takeout {takeout} from {nums}")
    nums.remove(takeout)
    print(f"nums {nums}")
    print_missing_number(nums)


if __name__ == "__main__":
    main()