雖然循環沒有中斷？

Question

我編寫了一個主腳本，它有一個包含 5 個不同選項的菜單，第五個選項是用戶是否想退出程序。 如果用戶在主菜單中鍵入 5，程序應該退出，但它沒有......它只是繼續循環瀏覽菜單。 誰能幫我解決這個問題？？

menuItems = np.array(["Load new data", "Check for data errors", "Generate plots", "Display list of grades","Quit"])

userinput = input("Please enter name of the data file: ")
grades = dataLoad(userinput)


while True:

    choice = displayMenu(menuItems)

    while True:
        if (choice == 1):
            userinput = input("Please enter name of the data file: ")
            grades = dataLoad(userinput)
            break


        elif (choice == 2):
            checkErrors(grades)
            break

        elif choice == 3:
            gradesPlot(grades)

        elif choice == 4:
            show = listOfgrades(grades)
            showList(show)

        elif (choice == 5):
            break


        else:
            print("Invalid input, please try again")
            break

Answer 1

在您的代碼中，當您調用 break 時，它會從內部 while 循環中斷並轉到外部 while 循環，這會導致整個過程再次進行。 如果在某些情況下您希望兩個 while 循環都中斷，那么您可以使用某種標志。

例子，

flag = False

while True:
    while True:
        if (1 == var):
            flag = True
            break
    if flag:
        break

//你的代碼

flag = False
while True:

    choice = displayMenu(menuItems)

    while True:
        if (choice == 1):
            userinput = input("Please enter name of the data file: ")
            grades = dataLoad(userinput)
            flag = True
            break


        elif (choice == 2):
            checkErrors(grades)
            flag = True
            break

        elif choice == 3:
            gradesPlot(grades)

        elif choice == 4:
            show = listOfgrades(grades)
            showList(show)

        elif (choice == 5):
            flag = True
            break


        else:
            print("Invalid input, please try again")
            flag = True
            break

    if True == flag:
        break

Answer 2

您有嵌套循環，並且break只中斷內部循環。

要解決此問題，請從else塊中刪除嵌套循環和break ：

while True:
    choice = displayMenu(menuItems)

    if (choice == 1):
        userinput = input("Please enter name of the data file: ")
        grades = dataLoad(userinput)
        break
    elif (choice == 2):
        checkErrors(grades)
        break
    elif choice == 3:
        gradesPlot(grades)
    elif choice == 4:
        show = listOfgrades(grades)
        showList(show)
    elif (choice == 5):
        break
    else:
        print("Invalid input, please try again")