month-hall-paradox.py

import random


class MontyHall:
    def __init__(self):
        self.prize_door = random.randint(1, 3)
        self.selected_door = 0
        self.opened_door = 0

    def select_door(self):
        self.selected_door = random.randint(1, 3)

    def host_door(self):
        # host door should not be the selected nor prize door
        d = random.randint(1, 3)
        while d in (self.selected_door, self.prize_door):
            d = random.randint(1, 3)
        self.opened_door = d

    def switch_door(self):
        # sum of door numbers = 1+2+3 = 6.
        self.selected_door = 6 - self.selected_door - self.opened_door

    def hit(self):
        if self.selected_door == self.prize_door:
            return True

    def run(self, switch=True):
        self.select_door()
        self.host_door()
        if switch:
            self.switch_door()
        return self.hit()  # hit?


# Switch
RUNS = 10000
print("%s Monty runs" % (RUNS))
hits = 0
for i in range(RUNS):
    monty = MontyHall()
    if monty.run(switch=True):
        hits += 1
print("Switch : %.1f%%" % (100.0 * hits / RUNS))

# Stay
hits = 0
for i in range(RUNS):
    monty = MontyHall()
    if monty.run(switch=False):
        hits += 1
print("Stay   : %.1f%%" % (100.0 * hits / RUNS))