The Monty Hall problem has annoyed me for a while. Not that I didn't understand it, the wiki page (http://en.wikipedia.org/wiki/MontyHallproblem) is quite extensive and explains it quite nicely, the problem is that I could never truely believe that by switching door, your chances of winning are 2/3 instead of 1/3 if you stick.
So I decided to test it.And you know what, it's true!
#!/usr/bin/python from random import randint # Monty Hall Problem Simulator # jsutton.co.uk 2014 # # This Python script simulates the Monty Hall Problem # http://en.wikipedia.org/wiki/Monty_Hall_problem # Modify 'runs' to change the number of iterations # Door Key # 0: Goat # 1: Car # 2: Removed Door ###### Functions ###### # Generate the three doors def generate_doors(): doors = [0,0,0] winning_door = randint(0,2) doors[winning_door] = 1 return doors # Return the index of the alternative door once # one has been chosen, and one removed def get_alternative_door(door_array, selected_door): for door_index, door in enumerate(door_array): if door_index is not selected_door: if door is not 2: return door_index # Return True or False if the selected door # Is a winning door def is_door_winner(door_array, selected_door): door_result = door_array[selected_door] if door_result is 0: return False elif door_result is 1: return True else: print("Something Strange Happened: ", door_result) return False # Returns True if swapping would have won def monty_cycle(): doors = generate_doors() selected_door = randint(0,2) door_removed = False while door_removed is False: for door_index, door in enumerate(doors): if door_index is not selected_door: if door is 0: rand = randint(0,1) if rand is 1: doors[door_index] = 2 door_removed = True break alternative_door = get_alternative_door(doors, selected_door) original_door_winner = is_door_winner(doors, selected_door) swapped_door_winner = is_door_winner(doors, alternative_door) return swapped_door_winner if __name__ == "__main__": results =  runs = 100 for i in range(runs): result = monty_cycle() results.append(result) total_success = sum(results) total_failure = runs - total_success tsp = (total_success / runs) * 100 tfp = (total_failure / runs) * 100 print("Total Runs: ", runs) print("Runs that won by swapping: ", total_success) print("Runs that won by staying: ", total_failure) print("Swap success: ", tsp, "%") print("Stay success: ", tfp, "%" )
Nothing complicated, it just generates a set of doors, sets a random door to be winner and then selects the 'chosen' door. Once the door has been chosen, a door is 'removed'. Then we look at whether switching would have resulted in a Win or a loss.
(True indicates switching would have won, whereas False indicates that staying would have won).
I did this for 100 runs and got this:
Total Runs: 100 Runs that won by swapping: 67 Runs that won by staying: 33 Swap success: 67.0 % Stay success: 33.0 %
Welp. I guess that settles it then!