from random import randint, choice
 
successes, attempts = 0, 0
 
while attempts < 1000:
    correct_door = randint(0, 2)
    players_door = randint(0, 2)
    unchosen_doors = [ x for x in [0,1,2] if x != players_door ]
    opened_door = choice(unchosen_doors)
    if opened_door == correct_door:
        # the opened door was the winning one, 
        # so we already lost before reaching the described scenario
        continue
 
    door_to_which_we_switch = 3 - players_door - opened_door
    attempts += 1
    if correct_door == door_to_which_we_switch: successes += 1
 
print(successes)

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