Python：通过while循环调用函数

Question

我正在尝试将我的程序扩展为将登录详细信息存储在字典中的程序，当您尝试登录时，它应该询问您的用户名和密码，以及登录详细信息是否与附加的匹配到字典中，它会说“您已登录！”，但我似乎根本无法调用我的 login() 函数，除了当我没有输入登录详细信息但它不会循环返回时打印出 else 打印语句到 menu() 就像它应该的那样，因为我把它放在一个 while 循环中。我想我在主程序中搞砸了我的while循环，但似乎无法理解它。帮助将不胜感激。

store = {}

def menu(): 
    mode = input("""Hello, below are the modes that you can choose from:\n
    ##########################################################################
    a) Login with login details
    b) Register login details
    To select a mode, enter the corresponding letter of the mode below
    ##########################################################################\n
    > """).strip()
    return mode

def login():
    if len(store) > 0 : #user has to append usernames and passwords before it asks for login details
        print("Welcome to the login console")
        while True:
            username = input ("Enter Username: ") 
            if username == "":
                print("User Name Not entered, try again!")
                continue
            password = input ("Enter Password: ") 
            if password == "":
                print("Password Not entered, try again!")
                continue
            try:
                if store[username] == password:
                    print("Username matches!")
                    print("Password matches!")
                    logged() #jumps to logged function and tells the user they are logged on
                    break 
            except KeyError: #the except keyerror recognises the existence of the username and password in the list
                print("The entered username or password is not found!")

    else:
        print("You have no usernames and passwords stored!")

def register(): #example where the username is appended. Same applies for the password
    print("Please create a username and password into the password vault.\n")

    while True:
        validname = True
        while validname:
            username = input("Please enter a username you would like to add to the password vault. NOTE: Your username must be at least 3 characters long: ").strip().lower()
            if not username.isalnum():
                print("Your username cannot be null, contain spaces or contain symbols \n")
            elif len(username) < 3:
                print("Your username must be at least 3 characters long \n")
            elif len(username) > 30:
                print("Your username cannot be over 30 characters \n")
            else:
                validname = False 
        validpass = True

        while validpass:
            password = input("Please enter a password you would like to add to the password vault. NOTE: Your password must be at least 8 characters long: ").strip().lower()
            if not password.isalnum():
                print("Your password cannot be null, contain spaces or contain symbols \n")
            elif len(password) < 8:
                print("Your password must be at least 8 characters long \n")
            elif len(password) > 20:
                print("Your password cannot be over 20 characters long \n")
            else:
                validpass = False #The validpass has to be True to stay in the function, otherwise if it is false, it will execute another action, in this case the password is appended.
        store[username] = password
        validinput = True
        while validinput:
            exit = input("\nEnter 'end' to exit or any key to continue to add more username and passwords:\n> ")
            if exit in ["end", "End", "END"]:
                menu()
                break
            else:
                validinput = False
                register()
        return register

def logged():
    print("----------------------------------------------------------------------\n")
    print("You are logged in!")


#Main routine

#The main program to run in a while loop for the program to keep on going back to the menu part of the program for more input till the user wants the program to stop
validintro = False 
while not validintro: 
        chosen_option = menu() #a custom variable is created that puts the menu function into the while loop
        validintro = True

        if chosen_option in ["a", "A"]:
            login()

        elif chosen_option in ["b", "B"]:
            register()

        else:
            print("""That was not a valid option, please try again:\n """)
            validintro = False

Answer 1

这是因为在打印“您没有存储用户名和密码！”之后，您返回到外部 while 但从未将 validintro 更改为 false。这会导致您的 while 循环结束。

您应该从 login 返回一个值以了解是否没有用户并在 while 中检查该值，或者在 login 函数中，在 else 部分将全局 validintro 设置为 false（我会推荐第一种方式。 )