HPMOR - Time-Turner prime numbers experiment

hpmor_primes.py

# Chapter 17 of HPMOR
# The experiment with prime numbers

# python doesn't support tail recursion, so do this with a while loop

def run(x, y):
    while True:
        # paper 2 is blank
        if x is None and y is None:
            x, y = 101, 101
        elif x == 997 and y == 997:
            x, y = None, None
        else:
            prod = x * y
            if prod == 181429:
                # Magic! Now you can compute prime factors of any prime number
                # I guess that 101 and 997 were chosen by the author[s] to set the lower and upper bound
                # Harry would have to continue the loop by sending the numbers back in time,
                # but we can stop our program
                print("{} x {} = 181429".format(x,y))
                return x, y
            else:
                x1 = x
                y1 = y + 2
                if y1 > 997:
                    x1 = x + 2
                    y1 = 101
                x, y = x1, y1

if __name__ == "__main__":
    # set initial numbers (try different variants)
    # 1. 101 x 101
    x, y = 101, 101
    # 2. blank paper
    #x, y = None, None

    run(x, y)