Simulate the classical game show problem of choosing one of three doors. One of the wrong doors are exposed, so what do you do? Stay, switch or randomly choose which to do? Try this a million times to see what the statistics say.

doors.py

#!/usr/bin/env python3

import random

def remove_door(doors, win, pick1):
    doors.remove(win)
    try:
        doors.remove(pick1)
        doors = [win, pick1]
    except ValueError:
        del doors[random.choice((0, -1))]
        doors.append(win)
    return doors

def test_prob() :

    doors = ['l', 'm', 'r']
    win = random.choice(doors)
    pick1 = random.choice(doors)

    doors = remove_door(doors, win, pick1)

    switch = [x for x in doors if x != pick1][0]
    pick2 = random.choice(doors)

    return (win == pick1, win == switch, win == pick2)

tries = 1000000
wins = [0, 0, 0]

for y in range(tries):
    result = test_prob()
    for i in range(3):
        if result[i]:
            wins[i] += 1

wins = [x/tries*100 for x in wins]

print("stay: {:.2f}%\nswitch: {:.2f}%\nrandom again: {:.2f}%".format(
    wins[0], wins[1], wins[2]))