如何修复由我在 Python 中的函数引起的这个无限循环？

Question

I've seemed to create a bank account log in system that works correctly. The only problem is that once a login is successful, the program would get stuck in a loop. For example: Say, I create my account and set my username as "Hello" and my password as "123".

The program will except these log in details but when I later try to log in with them, the infinite loop would happen.

I've tried amending this problem by plugging in return/global values for status and even put them in as many places in my program as possible but the infinite loop problem still persists. Could you please help me find why the loop keeps executing?

users = {}
status = ""

                            #--------------- Login menu -----------------#
def displayMenu():
    global status

    status = input("Are you a registered user? \n1 - Yes \n2 - No \nQ - Quit \n")  
    if status == '1':
        oldUser()
    elif status == '2':
        newUser()
    return status


def mainMenu():
    print("Hello account holder", login,"what service would  you like to use today?")

                            #---------- Screen for new users -------------#

def newUser():
    createLogin = input("Create login name: ")

    if createLogin in users: # check if login name exists
        print ("\nLogin name already exists!\n")
    else:
        createPassw = input("Create password: ")
        users[createLogin] = createPassw # add login and password
        print("\nAccount created!\n")     

                            #---------- Screen for old users -------------#

def oldUser():
    global login

    login = input("Enter login name: ")
    passw = input("Enter password: ")

    # check if user exists and login matches password
    if login in users and users[login] == passw:
        print("\nLogin successful!\n")
        mainMenu()

    else:
        print("\nUser doesn't exist or wrong password!\n")



# Main -------------------------------------------------------------------------------------------------------------


while status != "q":
    status = displayMenu()

Answer 1

Your code is working exactly as it is designed.

The main loop starts:

while status != "q":
    status = displayMenu()

Note that your program will only ever "quit" if the user gives an input of "q" in the displayMenu() , rather than "Q" . This can be fixed by checking status.lower() instead.

Then you specify that no, you are not a registered user by providing 2 as an input to the displayMenu() .

This brings you to newUser() , where you create your new account.

You'll then get returned to displayMenu() , where you can this time select 1 to login as a registered user, bringing you to oldUser() .

Once you enter your login credentials in oldUser() , you'll get brought to mainMenu() , where it will print the welcome message in mainMenu() , then return to oldUser() , then to displayMenu() , then back to the main loop.

Unless you're expecting something else to happen in mainMenu() , the only error here is that you're not normalizing the case of status before checking if it is "q" .