我的 python 代码有错误，但只是在 try-except 循环中。 [复制]

Question

我的 python 代码在 try-except 循环中有一些错误。如果您输入的输入不是“是”或“否”，它首先会打印“是”回复输出，然后在您回答问题后，如果您不输入“是”或“否”，它会显示输出。代码如下：

playAgain = None

while playAgain != "Yes" or "No" or "yes" or "no" or "y" or "n":
    try:
            playAgain = str(input("Do you want to play again? Enter Yes or No: "))         
            if playAgain == "Yes" or "y" or "yes":
                displayIntro()
            elif playAgain == "No" or "no" or "n":
                print("Oh, well. The magic 8 ball will see you next time...")
                sys.exit()
    except:
                print("That wasn't yes or no, idiot. The magic 8 ball will not give a fortune to such an imbocile.")

请帮忙，谢谢！

Answer 1

playAgain != "Yes" or "No" or "yes" or "no" or "y" or "n"

这不是正确的方法。

当您说playAgain != "Yes" 时，您需要对剩余的表达式执行相同的操作。所以一个有效的方法来做你打算做的事情如下：

playAgain != "Yes" or playAgain != "No" or playAgain != "yes" or playAgain != "no" or playAgain != "y" or playAgain != "n"

但这很丑而且太长了。

改为使用

playAgain not in ["Yes", "No", "yes", "no", "y", "n"]

在 Python 中，我们有一些方便的方法来处理此类问题。您可以使用in 运算符检查可能值列表中是否存在（或不存在）相关字符串。读起来也很好：“如果 playAgain (is) not in [this list of values]”。

您甚至可以操作输入，以便您更轻松地使用。也就是说，您降低所有字母并且不检查区分大小写的输入（如果您真的不关心区分大小写的输入；您真的关心是Yes 还是yEs？）：

playAgain.lower() not in ["yes", "y"]

应该这样做：

while True:
    playAgain = str(input("Do you want to play again? Enter Yes or No: "))         

    if playAgain.lower() in ["yes", "y"]:
        # do something with your yes input. Consider `break` out of the endless loop.
    elif playAgain.lower() in ["no", "n"]:
        # do something with your no input. Consider `break` out of the endless loop.
    else:
        print("That wasn't yes or no.")

请注意，上述循环是无限的。您需要根据您的程序逻辑进行突破。也就是说，当您需要跳出无限循环时，您需要在某处放置 break 语句。