Simulation of the Monty Hall / Game show problem

simulation.py

from abc import ABCMeta, abstractmethod
from random import choice


def game(player):
    # determine winning and loosing doors for this round
    doors = [1, 2, 3]
    winning_door = choice(doors)
    loosing_doors = [d for d in doors if d != winning_door]

    # let player pick a door
    player_choice = player.pick(doors)

    # remove a door
    doors = [d for d in doors if d == winning_door or d == player_choice]
    if len(doors) != 2:
        doors.append(choice(loosing_doors))

    # allow player to switch choice
    player_choice = player.switch(doors)

    # determine if the player won
    if player_choice == winning_door:
        return 'win'
    else:
        return 'lose'


class Player(metaclass=ABCMeta):

    @abstractmethod
    def pick(self, doors):
        ...

    @abstractmethod
    def switch(self, doors):
        ...


class RandomPlayer(Player):

    def pick(self, doors):
        return choice(doors)

    def switch(self, doors):
        return choice(doors)


class AlwaysKeepPlayer(Player):

    def pick(self, doors):
        self.my_choice = choice(doors)
        return self.my_choice

    def switch(self, doors):
        return self.my_choice


class AlwaysSwitchPlayer(Player):

    def pick(self, doors):
        self.my_choice = choice(doors)
        return self.my_choice

    def switch(self, doors):
        return [d for d in doors if d != self.my_choice][0]


def simulate(player_class, rounds=1000):
    wins = 0

    for _ in range(rounds):
        result = game(player_class())
        wins += 1 if result == 'win' else 0

    percent_wins = (wins / rounds) * 100
    print('{} won {:.1f}% of the time.'.format(
        player_class.__name__,
        percent_wins,
    ))


if __name__ == '__main__':
    simulate(RandomPlayer, rounds=10000)
    simulate(AlwaysKeepPlayer, rounds=10000)
    simulate(AlwaysSwitchPlayer, rounds=10000)