函数和if-else in python.多重条件.密码学

问题描述：

编写一个带有一个参数的函数shut_down(您可以使用任何您喜欢的东西；在这种情况下，我们将s用作字符串).

Write a function, shut_down, that takes one parameter (you can use anything you like; in this case, we'd use s for string).

shut_down函数在获取"Yes"，"yes"或"YES"作为参数时应返回"Shutting down..."，并在获取"No"，"no"或"NO"时返回"Shutdown aborted!". 如果得到的不是这些输入，函数应返回"Sorry, I didn't understand you."

The shut_down function should return "Shutting down..." when it gets "Yes", "yes", or "YES" as an argument, and "Shutdown aborted!" when it gets "No", "no", or "NO". If it gets anything other than those inputs, the function should return "Sorry, I didn't understand you."

我到目前为止编写的代码如下.它会出错，例如以"No"作为参数，它不会按预期方式返回"Shutdown aborted!".

The code I wrote so far is below. It makes errors, e.g. given "No" as the argument, it does not return "Shutdown aborted!" as expected.

def shut_down(s):
    if s == "Yes" or "yes" or "YES":
        return "Shutting down..."
    elif s == "No" or "no" or "NO":
        return "Shutdown aborted!"
    else:
        return "Sorry, I didn't understand you."

答

此:

s == "Yes" or "yes" or "YES"

等效于此:

(s == "Yes") or ("yes") or ("YES")

由于非空字符串为True，因此它将始终返回True.

Which will always return True, since a non-empty string is True.

相反，您希望分别将s与每个字符串进行比较，如下所示:

Instead, you want to compare s with each string individually, like so:

(s == "Yes") or (s == "yes") or (s == "YES")  # brackets just for clarification

它应该像这样结束:

def shut_down(s):
    if s == "Yes" or s == "yes" or s == "YES":
        return "Shutting down..."
    elif s == "No" or s == "no" or s == "NO":
        return "Shutdown aborted!"
    else:
        return "Sorry, I didn't understand you."

函数和if-else in python.多重条件.密码学

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