While循环以检查有效的用户输入？

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 = Truewhile 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) ychoice = yEnjoying the course? (y/n) nchoice = yinput = nSorry, I didn't catch that. Enter again:Enjoying the course? (y/n) xchoice = yinput = xSorry, 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

一个解决方案

!=

，并

loop_condition

如果必须同时使用

!=

loop_condition

student_surveypromptOn = Truewhile 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）。