Python猜拳游戏while循环条件异常：无法在一方得分达3时终止

问题描述 #

编写的Python猜拳游戏期望当玩家（score_player）或电脑（score_computer）任意一方得分达到3时终止该局游戏，但实际运行时，游戏会持续到双方得分均≥3甚至一方得分超过3才停止，询问while循环条件未正确执行的原因。

原代码：

import random

while True:
    score_player = 0
    score_computer = 0

    while score_computer <= 2 or score_player <= 2:
        choices = ['rock', 'scissors', 'paper']
        player = None
        computer = random.choice(choices)

        while player not in choices:
            player = input('rock,scissors or paper? : ').lower()

        print('computer:', computer)
        print('player: ', player)

        if player == computer:
            print('You are tied!')
        elif player == 'rock':
            if computer == 'scissors':
                score_player += 1
            elif computer == 'paper':
                score_computer += 1

        elif player == 'scissors':
            if computer == 'paper':
                score_player += 1
            elif computer == 'rock':
                score_computer += 1

        elif player == 'paper':
            if computer == 'rock':
                score_player += 1
            elif computer == 'scissors':
                score_computer += 1

        print('Score_player : ', score_player)
        print('Score_computer', score_computer)


    playe_again = input('Do you want to continue? (Yes/No) :').lower()
    #while playe_again == 'yes' or 'no':
    if playe_again != 'yes':
        break
print('I hope you have enjoyed the game!')

问题原因 #

核心问题出在内层while循环的条件判断逻辑错误：

while score_computer <= 2 or score_player <= 2:

这里使用or运算符的含义是：只要电脑得分≤2 或者 玩家得分≤2，循环就会继续执行。也就是说，只有当电脑得分>2 并且 玩家得分>2时，循环才会终止——这完全和你“任意一方到3分就终止”的需求相反。

你的需求是：只要有一方得分达到3（即>2）就停止该局游戏，因此循环应该在双方得分都未达到3时才继续，需要把or替换为and：

while score_computer <= 2 and score_player <= 2:

这样只要任意一方得分≥3，循环条件就不成立，游戏会立即终止当前对局。

修正后的代码 #

import random

while True:
    score_player = 0
    score_computer = 0

    # 修改循环条件为and，双方都未到3分时才继续游戏
    while score_computer <= 2 and score_player <= 2:
        choices = ['rock', 'scissors', 'paper']
        player = None
        computer = random.choice(choices)

        while player not in choices:
            player = input('rock,scissors or paper? : ').lower()

        print('computer:', computer)
        print('player: ', player)

        if player == computer:
            print('You are tied!')
        elif player == 'rock':
            if computer == 'scissors':
                score_player += 1
            elif computer == 'paper':
                score_computer += 1

        elif player == 'scissors':
            if computer == 'paper':
                score_player += 1
            elif computer == 'rock':
                score_computer += 1

        elif player == 'paper':
            if computer == 'rock':
                score_player += 1
            elif computer == 'scissors':
                score_computer += 1

        print('Score_player : ', score_player)
        print('Score_computer', score_computer)


    play_again = input('Do you want to continue? (Yes/No) :').lower()
    if play_again != 'yes':
        break
print('I hope you have enjoyed the game!')

额外细节修正 #

原代码中有一个拼写错误：playe_again改为play_again，虽然不影响运行，但修正后代码更规范。

内容的提问来源于stack exchange，提问作者user21743456