python 中的废话

Question

我正在尝试模拟 n 场双骰子游戏。该代码对我来说似乎很有意义，但我从未得到正确的结果。例如，如果我输入 n = 5，即五场比赛，则胜利和失败的总和大于 5。

它的工作原理如下：如果初始掷骰子数为 2、3 或 12，则玩家失败。如果掷骰结果为 7 或 11，则玩家获胜。任何其他初始掷骰都会导致玩家再次掷骰。他继续掷骰，直到掷出 7 或初始掷骰的值。如果他在掷出 7 之前重新掷出初始值，则获胜。首先掷出 7 就输了。

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

问题在于 相反

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

，它应该

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

在您的代码中，您正在模拟两个游戏而不是一个（通过调用 game() 两次）。这给出了四种可能的结果，而不是两种（赢/输），从而给出了不一致的总体结果。

Answer 2

在此代码中，

for i in range(n):
    if game():
        wins = wins + 1
    if not game():
        losses = losses + 1

您调用了 game() 两次，因此您在那里玩了两个游戏。您想要的是 else 块：

for i in range(n):
    if game():
        wins = wins + 1
    else:
        losses = losses + 1

顺便说一句，您可以使用 in 简化逻辑：

def game():
    dice = roll()

    if dice in (2,3,12):
        return False

    if dice in (7,11):
        return True

    # keep rolling
    while True:
        new_roll = roll()

        # re-rolled the initial value => win
        if new_roll==dice:
            return True

        # rolled a 7 => loss
        if new_roll == 7:
            return False

        # neither won or lost, the while loop continues ..

代码实际上就是您给出的描述。

Answer 3

不要这样做，

    for i in range(n):
        if game():
            wins = wins + 1
        if not game():
            losses = losses + 1

效果根本不好。

Answer 4

这段代码有很多问题。最重要的是，每个循环都会调用 game() 两次。您需要调用它一次并存储结果，然后基于该结果进行切换。

Answer 5

面向对象的重写：

import random

try:
    rng = xrange   # Python 2.x
    inp = raw_input
except NameError:
    rng = range    # Python 3.x
    inp = input

def makeNSidedDie(n):
    _ri = random.randint
    return lambda: _ri(1,n)

class Craps(object):
    def __init__(self):
        super(Craps,self).__init__()
        self.die = makeNSidedDie(6)
        self.firstRes = (0, 0, self.lose, self.lose, 0, 0, 0, self.win, 0, 0, 0, self.win, self.lose)
        self.reset()

    def reset(self):
        self.wins   = 0
        self.losses = 0

    def win(self):
        self.wins += 1
        return True

    def lose(self):
        self.losses += 1
        return False

    def roll(self):
        return self.die() + self.die()

    def play(self):
        first = self.roll()
        res   = self.firstRes[first]
        if res:
            return res()
        else:
            while True:
                second = self.roll()
                if second==7:
                    return self.lose()
                elif second==first:
                    return self.win()

    def times(self, n):
        wins = sum(self.play() for i in rng(n))
        return wins, n-wins

def main():
    c = Craps()

    while True:
        n = int(inp("How many rounds of craps would you like to play? (0 to quit) "))
        if n:
            print("Won {0}, lost {1}".format(*(c.times(n))))
        else:
            break

    print("Total: {0} wins, {1} losses".format(c.wins, c.losses))

if __name__=="__main__":
    main()