Simulation of the Monty Hall problem

gistfile1.py

import random

def setup_doors():
    doors = [0] * 3
    doors[random.choice(range(3))] = 1
    return doors

def select():
    return random.choice(range(3))


def reveal_goat(doors, selected):
    candidates = [i for i, v in enumerate(doors) if i != selected and v == 0]
    return random.choice(candidates)

def win_after_switch():
    doors = setup_doors()
    selected = select()
    revealed = reveal_goat(doors, selected)
    switch_to = ({0, 1, 2} - {selected, revealed}).pop()
    return doors[switch_to] == 1
    
if __name__ == '__main__':
    print(sum(1 for i in xrange(100000) if win_after_switch()))

In [42]: 2.0 / 3
Out[42]: 0.6666666666666666

In [43]: sum(1 for i in xrange(10000) if play())
Out[43]: 6684

In [44]: sum(1 for i in xrange(10000) if play())
Out[44]: 6732

In [45]: sum(1 for i in xrange(10000) if play())
Out[45]: 6666