Question

这是我试图循环的地方，如果他们不输入b或c他们将得到错误输出，因此将不得不回到问题。虽然这不起作用： 已更新

if get_bool_input("Do you wish to view the previous results from your class: "): #The 'get_bool_input' will determine if they input yes or no and will either open the file or not.
    selection= input("Do you wish to view the results in Alphabetical order(A), scores highest to lowest(B) or average score highest to lowest?(C)")
    while True:
        if selection not in ['A', 'B', 'C']:
            print ("Error, type in A, B or C.")
            break
        if selection == 'A':
            print (alphabetically(data))
            break
        elif selection == 'B':
            print (by_score(data))
            break
        elif selection == 'C':
            print (by_average(data))  
            break

else:
    input ("Press any key to exit")

输出

Do you wish to view the previous results from your class: yes
Do you wish to view the results in Alphabetical order(A), scores highest to lowest(B) or average score highest to lowest?(C)n
Error, type in A, B or C.

我没有选择输入另一个答案。

Answer 1

您有四个问题：return True在函数之外的语法无效，即使它位于elif和else之间，else: selection not in ['A', 'B', 'C']:也不是有效的语法，您永远不会重新定义selection。也许你想要更像这样的东西：

while True:
    selection = input("Do you wish to view the results in Alphabetical order(A), scores highest to lowest(B) or average score highest to lowest?(C)")
    if selection not in ['A', 'B', 'C']:
        print ("Error, type in A, B or C.")
        continue
    if selection == 'A':
        print (alphabetically(data))
    elif selection == 'B':
        print (by_score(data))
    elif selection == 'C':
        print (by_average(data))  
    break

Answer 2

您的else语句永远不会被执行。你的return True语句会削减那里的执行流程。

您可能希望这样：

while True:
    selection= input("Do you wish to view the results in Alphabetical order(A), scores highest to lowest(B) or average score highest to lowest?(C)")
    if selection == 'A':
        print (alphabetically(data))
        return True
    elif selection == 'B':
        print (by_score(data))
        return True #replace this with 'break' if you're not inside a function
    elif selection == 'C':
        print (by_average(data))
        return True  
    else:
        print ("Error, type in A, B or C.")

循环和一些帮助循环

2 个答案: