Python中的石头剪刀布

Question

我正在尝试写一个Python程序，但我在获取分数时遇到了困难。我把它写成了一个返回值的函数，每次运行程序时，它似乎都会跳过获取分数的那一步，除非我加上一个else语句，这样它就会自动跳到else语句那里。
我会把完整的代码附在下面。
非常感谢任何帮助，我很感激！
这是我第一次在这个论坛发帖，如果我搞错了什么，我很抱歉。

#constants
Rock = 1
Paper = 2
Scissors = 3

#Define the main function
def main():

    #set control loop
    keep_going = 'Y'


    #set counter to zero
    computer_wins = 0
    player_wins = 0
    tie_score = 0

    #call display message
    display_message()

    while keep_going == 'y' or keep_going == 'Y':

        play_game()


        #prompt user to keep going
        keep_going = input('would you like to play again? (Y for Yes): ')

    print('The computer won', computer_wins, 'times')
    print('The player won', player_wins, 'times')
    print('There were', tie_score, 'tie scores')

def play_game():

    #get random input
    computer = get_random()

    #get the players input
    play = get_play()

    #validate input
    if play == '1' or play == '2' or play == '3':
        play == True
    else:
        play == False
        print('Error: Invalid Entry')
        play = input('Please enter 1 for Rock, 2 for Paper, or 3 for Scissors: ')

    if play == computer:
        print('Tie Score, Please try again')
        tie_score += 1

    else:
        get_score(computer, play)

    print('The computer chose:', computer)
    print('The player chose: ', play)


#define display message
def display_message():
    print('Welcome to Rock Paper Scissors, a game of chance to see who will')
    print('outsmart the other. This game is Man VS Computer.')
    print('The program will select a random integer and then ask you for an integer')
    print('1 for Rock 2 for paper or 3 for Scissors. The program will then tell')
    print('you who won the game.')
    print('GOOD LUCK!')
    print
    print

def get_random():
    import random

    #generate random int
    computer = random.randint(1, 3)
    return computer


def get_play():
    #prompt user to enter an integer 1, 2, or 3
    play = input('Select 1 for Rock, 2 for Paper, or 3 for Scissors: ')
    return play

def get_score(computer, play):

    if computer == 1 and play == 2:
        score = 'player wins'
        print('Paper covers Rock, Player Wins')
        #player wins
        player_wins += 1

    elif computer == 1 and play == 3:
        score = 'computer wins'
        print('Scissors cut Paper, Computer Wins')
        #computer wins
        computer_wins += 1


    elif computer == 2 and play == 1:
        score = 'computer wins'
        print('Paper covers Rock, Computer Wins')
        #computer wins
        computer_wins += 1

    elif computer == 2 and play == 3:
        score = 'player wins'
        print('Scissors cut Paper, Player Wins')
        #player wins
        player_wins += 1


    elif computer == 3 and play == 1:
        score = 'player wins'
        print('Rock smashes Scissors, Player Wins')
        #player wins
        player_wins += 1

    elif computer == 3 and play == 2:
        score = 'computer wins'
        print('Scissors cut Paper, Computer Wins')
        #computer wins
        computer_wins += 1


#call main function
main()

Answer 1

这里有几个快速的注意事项，都是我快速浏览代码时想到的：

在 get_score() 函数里，你可以加一个 else 条件来处理平局的情况，这样在 play_game() 函数里就不需要专门去检查了。

把 import random 移到文件的最上面。一般来说，导入的模块都是放在文件开头的。而且每次想要随机数时，不需要重复导入。

不太确定这是不是个笔误，因为 play 似乎总是一个整数，但你在 play_game() 里用到了 play == True 和 play == False。如果你想让 play 只包含 True 或 False，你应该用一个等号，比如 play = True。不过这看起来不太合理，因为你在把 play 和 computer 比较，像是在比较整数一样。

另外，你在 get_score() 方法里想用 score 变量做什么呢？

哦，如果你让 get_score() 方法返回一些信息，告诉你谁赢了比赛，那会很有帮助。因为 computer_wins 和 player_wins 是在 main() 里定义的，所以在 get_score() 方法里是无法访问的。一个简单的方法是从 get_score() 返回一个整数。这是一种比较 C 风格的处理方式（返回 -1/0/1）。可以像这样写（伪代码）：

def get_score():
  score = 0
  if computer wins:
      score = -1
  elif player wins:
      score = 1

  return score


winner = get_score()
if winner == 0:
    print 'tie game'
elif winner == 1
    print 'the player won'
else:
    print 'the computer won'

Answer 2

我单独回答了你的问题，不过为了好玩，这里有一个简单的石头、剪刀、布游戏的代码可以看看。这个代码是为Python 2.x写的，可能在Python 3中无法运行，但对你或者将来有需要的人可能会有帮助。

# "Rock, Paper, Scissors" demo for Python 2.x
# by Dan Kamins

import random

ROCK = 1
PAPER = 2
SCISSORS = 3

NAMES = { ROCK: 'Rock', PAPER: 'Paper', SCISSORS: 'Scissors' }
WHAT_BEATS_WHAT = { ROCK: SCISSORS, PAPER: ROCK, SCISSORS: PAPER }
WIN_ACTIONS = { ROCK: 'crushes', PAPER: 'smothers', SCISSORS: 'cuts' }

score_player = 0
score_computer = 0
score_ties = 0

def main():
    intro()
    while main_loop():
        pass
    summary()

def intro():
    print "Welcome to Rock, Paper, Scissors!"

def main_loop():
    player = get_player_input()
    computer = random.randint(1, 3)
    check_result(player, computer)
    return ask_play_again()

def check_result(player, computer):
    global score_player, score_computer, score_ties
    if player == computer:
        print "Tie!  Computer also chose {0}.".format(NAMES[computer])
        score_ties += 1
    else:
        if WHAT_BEATS_WHAT[player] == computer:
            print "Your massive {0} {1} the computer's {2}!".format(
                NAMES[player], WIN_ACTIONS[player], NAMES[computer])
            score_player += 1
        else:
            print "The computer's {0} {1} your pathetic {2}!".format(
                NAMES[computer], WIN_ACTIONS[computer], NAMES[player])
            score_computer += 1

def ask_play_again():
    again = raw_input("Enter Y to play again: ")
    return again in ('y', 'Y')

def get_player_input():
    while True:
        print
        player = raw_input("Enter 1 for Rock 2 for paper or 3 for Scissors: ")
        try:
            player = int(player)
            if player in (1,2,3):
                return player
        except ValueError:
            pass
        print "Please enter a number from 1 to 3."

def summary():
    global score_player, score_computer, score_ties
    print "Thanks for playing."
    print "Player won: ", score_player
    print "Computer won: ", score_computer
    print "Ties: ", score_ties

if __name__ == '__main__':
    main()

Answer 3

这段代码有很多问题，让人不知道从哪里开始说起（不过别灰心）……

首先，看起来你在用的是Python 3（主要是因为你用到了input而不是raw_input，还有你在打印时用的括号），这会限制你能得到的帮助。大多数人还是在用Python 2.6或2.7。不过，先不说这个……

接下来，关于你提问的主要问题有：

第一：你在处理玩家输入时用的是字符串（比如 '1', '2', '3'），而计算机选择的是数字（比如 1, 2, 3）。所以你需要以相同的方式进行比较。换句话说，不要这样：

if computer == 1 and play == 2:

你应该这样写：

if computer == 1 and play == '2':

第二：你试图在一个函数中引用另一个函数的变量，这样是行不通的。如果你想让computer_wins等变量是全局的，你需要在全局范围内初始化它们，比如在你声明"#constants"之后，进入main之前。然后在任何使用这些变量的函数中，你必须写global computer_wins来表明它们是全局变量，而不是局部变量。

解决了这些问题后，代码应该会好一些，但你仍然需要做很多整理和继续努力！

坚持下去，很快这就会变得很自然了。