Monte Carlo Simulation for the Monty Hall Problem with only Three Doors

import random, sys

TRIALS = 1000    # trials per strategy (swap and don't swap)

def test_swap():
  door_list = [0, 0, 1]
  random.shuffle(door_list)
  rand_doors = dict(zip([0, 1, 2], door_list))    # create the doors
  door_num = random.choice(list(rand_doors.keys()))    # choose a door
  
  if rand_doors[door_num]:    # if you chose the prize door
    # You lose the prize because the host one of the goat doors,
    # and you swap from the prize door to the other goat door
    return False
  elif not rand_doors[door_num]:    # if you chose a goat door
    # You win the prize because the host the other goat
    # door, and you swap from your goat door to the prize door
    return True

def test_no_swap():
  door_list = [0, 0, 1]
  random.shuffle(door_list)
  rand_doors = dict(zip([0, 1, 2], door_list))    # create the doors
  door_num = random.choice(list(rand_doors.keys()))    # choose a door
  
  if rand_doors[door_num]:    # if you chose the prize door
    # You win the prize because the host eliminates one
    # of the goat doors, but you keep the prize door
    return True
  elif not rand_doors[door_num]:    # if you chose a goat door
    # You lose the prize because the host eliminates the
    # other goat door, but you keep your original goat door
    return False

##################################################################
###                         Main Script                        ###
##################################################################

if sys.version_info[0] == 2: print 'Running ...',
elif sys.version_info[0] == 3: exec("print('Running...', end=' ')")

swap_wins, no_swap_wins = 0, 0

for i in range(TRIALS):
  if test_swap():
    swap_wins += 1
  if test_no_swap():
    no_swap_wins += 1

print('Done')
print('Not swapping doors won you {} prizes out of {} ({}%)'.format(no_swap_wins, TRIALS, str(float(no_swap_wins) / TRIALS * 100)[:5]))
print('Swapping doors won you {} prizes out of {} ({}%)'.format(swap_wins, TRIALS, str(float(swap_wins) / TRIALS * 100)[:5]))

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