While循环以检查有效的用户输入？

Question

这里的Python新手非常抱歉，我确定这是一个愚蠢的问题，但是我似乎无法在要求我使用while循环检查有效用户输入的教程中解决以下挑战。

（使用Python2.7）

这是我的代码，但无法正常工作：

choice = raw_input('Enjoying the course? (y/n)')
student_surveyPromptOn = True
while student_surveyPromptOn:
    if choice != raw_input('Enjoying the course? (y/n)'):
        print("Sorry, I didn't catch that. Enter again: ")
    else:
        student_surveyPromptOn = False

上面打印输出到控制台：

Enjoying the course? (y/n) y
Enjoying the course? (y/n) n
Sorry, I didn't catch that. Enter again: 
Enjoying the course? (y/n) x
Sorry, I didn't catch that. Enter again: 
Enjoying the course? (y/n)

这显然是不正确的-循环应该在用户输入“ y”或“ n”时结束，但是我不确定如何执行此操作。我在这里做错了什么？

注意：挑战要求我同时使用!=运算符和loop_condition

Answer 1

较短的解决方案

while raw_input("Enjoying the course? (y/n) ") not in ('y', 'n'):
    print("Sorry, I didn't catch that. Enter again:")

您的代码在做什么错

关于您的代码，您可以添加一些打印内容，如下所示：

choice = raw_input("Enjoying the course? (y/n) ")
print("choice = " + choice)
student_surveyPromptOn = True
while student_surveyPromptOn:
    input = raw_input("Enjoying the course? (y/n) ")
    print("input = " + input)
    if choice != input:
        print("Sorry, I didn't catch that. Enter again:")
    else:
        student_surveyPromptOn = False

上面打印出：

Enjoying the course? (y/n) y
choice = y
Enjoying the course? (y/n) n
choice = y
input = n
Sorry, I didn't catch that. Enter again:
Enjoying the course? (y/n) x
choice = y
input = x
Sorry, I didn't catch that. Enter again:
Enjoying the course? (y/n)

如您所见，代码中的第一步是出现问题，答案将初始化的值choice。这就是你做错了。

一个解决方案!=，并loop_condition

如果必须同时使用!=运算符和，loop_condition则应编写代码：

student_surveyPromptOn = True
while student_surveyPromptOn:
    choice = raw_input("Enjoying the course? (y/n) ")
    if choice != 'y' and choice != 'n':
        print("Sorry, I didn't catch that. Enter again:")
    else:
        student_surveyPromptOn = False

但是，在我看来，Cyber​​的解决方案和我较短的解决方案都更优雅（例如，更Python化）。