在接受输入之前，需要对照列表检查输入的raw_input问题

Question

对外面的人来说，这会很简单，但对我来说，对于一个基本的新手来说，这让我头疼。

我需要一个用户输入一个教育等级A，B，C，D，E或F。

我希望小写或大写都是可以接受的，但对于任何其他输入值，它都要循环，直到它们循环为止。

到目前为止，我已经这样写了：

grades = (raw_input("Please enter your educational grade either as A, B, C, D, E or F: "))

# checking for truthiness
while grades != ("A", "a", "B", "b", "C", "c", "D", "d", "E", "e", "F", "f"):
    print ("The grade you entered does not conform.")
    grades = (raw_input("Please enter your educational grade either as A, B, C, D, E or F: "))

# display valid input
print ("Your input is valid, you entered:  "), grades

谢谢，克里斯

Answer 1

使用str.upper()或str.lower()可以检查用户输入，但与while循环中的列表中使用的情况相匹配是一致的。这有点重复/多余，但我认为满足了您的要求：

grades = raw_input("Please enter your educational grade either as A, B, C, D, E or F: ").upper()

while grades not in(["A", "B", "C", "D", "E", "F"]): 
    print ("The grade you entered does not conform.")
    grades = raw_input("Please enter your educational grade either as A, B, C, D, E or F: ").upper()

print ("Your input is valid, you entered: "), grades

或者，一个while True:循环版本完成相同的任务，但在循环中移动提示用户输入，从而减少代码重复。

while True:
    grades = raw_input("Please enter your educational grade either as A, B, C, D, E or F: ").upper()
    if grades not in(["A", "B", "C", "D", "E", "F"]):
        print ("The grade you entered does not conform.")
    else:
        print ("Your input is valid, you entered: "), grades
        break