Question

I’m trying to simulate n games of craps. The code seems to make sense to me but I never get the right result. For example, if I put in n = 5 i.e. fives games the wins and losses sum to something greater than 5.

Here’s how it’s supposed to work: if initial roll is 2, 3, or 12, the player loses. If the roll is 7 or 11, the player wins. Any other initial roll causes the player to roll again. He keeps rolling until either he rolls a 7 or the value of the initial roll. If he re-rolls the initial value before rolling a 7, it’s a win. Rolling a 7 first is a loss.

from random import randrange

    def roll():
        dice = randrange(1,7) + randrange (1,7)
        return dice

    def sim_games(n):
        wins = losses = 0
        for i in range(n):
            if game():
                wins = wins + 1
            if not game():
                losses = losses + 1
        return wins, losses

    #simulate one game

    def game():

            dice = roll()
            if dice == 2 or dice == 3 or dice == 12:
                return False
            elif dice == 7 or dice == 11:
                return True
            else:
                dice1 = roll()
                while dice1 != 7 or dice1 != dice:
                    if dice1 == 7:
                        return False
                    elif dice1 == dice:
                        return True
                    else:
                        dice1 = roll()

    def main():

        n = eval(input("How many games of craps would you like to play? "))
        w, l = sim_games(n)

        print("wins:", w,"losses:", l)

Answer 1

The problem is with

        if game():
            wins = wins + 1
        if not game():
            losses = losses + 1

Instead, it should be

        if game():
            wins = wins + 1
        else:
            losses = losses + 1

In your code, you are simulating two games instead of one (by calling game() twice). This gives four possible outcomes instead of two (win/loss), giving inconsistent overall results.