python-3.x - python : Unable to terminate loop with different type of variable

Question

我制作了一个程序来存储您输入的登录详细信息，并允许您使用它登录到菜单的主要部分。例如，当所有数据类型都是字符串时，一切都运行良好； modea = input("Etc")为了允许用户通过输入与选项相对应的数字输入来选择选项，例如“2”，它应该在满足 if modea == 2 时调用其分配的函数。语句，但如果我尝试将字符串更改为整数数据类型，例如 modea = int(input("Etc")) ，即使我输入了预期的输入，循环也永远不会停止并继续运行，就好像我什么都没输入一样，这与简单地使用 modea = input("etc") 相反它将所有内容都视为一个字符串，它仍然会接受数字输入并执行其分配的操作，但如果数据类型是整数则不会？

我在这里添加了完整的代码以使其更有意义，大多数代码都可以按预期运行而被忽略，但我似乎无法理解 logged() 是怎么回事。我试图获取 modea = int(input("etc")) 的代码的功能部分通过在满足 if 语句时终止其循环来工作，但它只是继续循环，就好像一切都为空一样。帮助将不胜感激。

#import modules
import time
import sys
import re

#Initialise variables that could help with error handling
name = ""
mode = ""
username = ""
password = ""
addusername = ""
addpassword = ""
exit = ""
modea = ""
new_app = ""
new_pass = ""
quit = ""

#Dictionary to store more than one set of login details
vault = {}

#Lists to store website names and passwords
appvault = []
passvault = []


#FIRST MENU AND REGISTERING LOGIN DETAILS -----------------------------------------------------------------------------------------------------------------------------------------

def menu(): #The menu function is the 1st menu that asks the user to either register their login details or to login with existing login details saved into the vault dictionary
    print("--------------------------*ENTERING THE MAIN MENU*-----------------------------------\n") #triple """ used to effectively format the menu
    mode = input(str("""Hello {}, below are the modes that you can choose from:\n 
    ##########################################################################
    a) Login with username and password
    b) Register as a new user
    To select a mode, enter the corresponding letter of the mode below
    ##########################################################################\n
    > """.format(name))).strip() #greets user and removes any white space
    return mode #returns the input

def login(username, password): #The login function is where the user logins in with existing registered details in the vault dictionary
    if len(vault) > 0 : #user has to append usernames and passwords before it asks for login details
        print("Welcome {} to the login console".format(name))
        noloop = True #Starts a loop if True will begin looping
        while noloop:
            addusername = input("Please enter username: ") 
            if addusername == "":
                print("Username not entered, try again!")
                continue #returns to the beginning of the while loop if null
            addpassword = input("Please enter password: ") 
            if addpassword == "":
                print("Password not entered, try again!")
                continue #returns to the beginning of the while loop if null
            try:
                if vault[addusername] == addpassword: #If the username and password match with the login details appended into the dictionary, it will count as matching details.
                    print("Username matches!")
                    print("Password matches!")
                    print("Logging into password vault...\n")
                    noloop = logged() #jumps to logged function and tells the user they are logged on
                    return noloop #to return the noloop depending on users option (True or False)
            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!") #When the user selects option A before adding any login details to the dictionary
        return True #returning to the start of the loop when the else statement is printed

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

    while True:
        validname = True #whileloop will loop the username variable and while True it runs the loop
        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(): #handles usernames with no input, contain spaces between them or have symbols in them.
                print("Your username cannot be null, contain spaces or contain symbols \n")
            elif len(username) < 3: #any username with less than 3 characters is rejected and looped back
                print("Your username must be at least 3 characters long \n")
            elif len(username) > 30: #any username with more than 30 characters is rejected and looped back
                print("Your username cannot be over 30 characters long \n")
            else:
                validname = False #whileloop is False will mean the loop will break and proceed onto asking password
        validpass = True #whileloop will loop the password variable and while True it runs the loop

        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(): #handles null input passwords, passwords that contain spaces or symbols
                print("Your password cannot be null, contain spaces or contain symbols \n")
            elif len(password) < 8: #passwords that are less than 8 characters long are rejected and loops back
                print("Your password must be at least 8 characters long \n")
            elif len(password) > 20: #passwords that are more than 20 characters long are rejected and loops back
                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.
        vault[username] = password #the appending process of username and passwords to the dictionary
        validinput = True #whileloop asking for the user if they want to quit or add more login details
        while validinput:
            exit = input("\nDo you want to register more usernames and passwords? Enter 'end' to exit or any key to continue to add more username and passwords:\n> ")
            if exit in ["end", "End", "END"]: #if input matches these conditions, the loop will then break and thus jump back to the main menu
                return #returns outputs to the called function
            else:
                validinput = False #if user decides not to quit and to add more login details, then register is called and the process of asking for login input repeats
                register()
        return register #returns login details to the function


#LOGGED ONTO THE PASSWORD AND WEBSITE APP ADDING CONSOLE------------------------------------------------------------------------------------------------------------------------

def logged(): #The logged function is the 2nd menu where the user is able to access after logging in with their registered login details
    print("-----------------------------*ENTERING THE PASSWORD VAULT MENU*-----------------------------------\n")
    print("You are logged in, welcome to the password vault console.")
    keeplooping = True #whileloop that is True will keep the menu in a loop
    while keeplooping:    
        try:
            modea = int(input("""Below are the options you can choose from in the password vault console:
            ##########################################################################\n
            1) Find the password for an existing website/app
            2) Add a new website/app and a new password for it
            3) Summary of the password vault
            4) Exit
            ##########################################################################\n
            > """))
        except ValueError:
            print("Please enter a valid option!")

    if modea == 1: #if the user enters 1 as instructed, then they have decided to choose to find existing apps and passwords
        viewapp() #viewapp function is called

    elif modea == 2: #if user enters 2 as instructed, then they have decided to add new app/websites and the passwords for it
        addapp() #addapp function is called

    elif modea == 3: #if the user enters 3 as instructed, then they have decided to look at the summary of passwords entered so far
        summary() #summary function is called

    elif modea == 4: #if the user enters 4 as instructed, then they have deicided to quit the entire program. All loops stop and program ends with print statement saying "Goodbye"
        keeplooping = False 
        print("*Exiting program*\n")
        time.sleep(2)
        print("############################################################")
        print("Goodbye user and thanks for using the password vault program")
        print("############################################################")
        return keeplooping 
    else:
        print("That was not a valid option, please try again: ") 
        validintro = False 


def viewapp(): #The viewapp function is the 1st option of the password and vault menu that allows the user to view the app/websites and passwords stored so far
    if len(appvault) > 0: #The website/apps and passwords are only shown once the user has entered a set of the info, otherwise no info will be shown
        print("""Below are the details of the website/apps and passwords stored so far: 
(NOTE: Websites/apps and passwords are shown in order of being appended; 1st password is for 1st website, etc...\n""")
        for app in appvault: 
            print("Here are the website/app you have stored:")
            print("- {}\n".format(app)) #Website/app is printed out here
    if len(passvault) > 0 : #The website/apps and passwords are only shown once the user has entered a set of the info, otherwise no info will be shown
        for code in passvault: 
            print("Here are the password you have stored for the websites/apps: ")
            print("- {}\n".format(code)) #The passwords are printed out here

    else:
        print("You have no apps or passwords entered yet!") 

def addapp(): 
    while True:
        validapp = True 
        while validapp:
            new_app = input("Enter the new website/app name: ").strip().lower()
            if len(new_app) > 20: #if the user enters a website with more than 20 characters, it is rejected and loops back and asks for input again
                print("Please enter a new website/app name with no more than 20 characters: ")
            elif len(new_app) < 1: #if the user enters nothing, program loops back and asks for input again
                print("Please enter a valid new website/app name: ")
            else:
                validapp = False 
                appvault.append(new_app)

        validnewpass = True 
        while validnewpass:
            new_pass = input("Enter a new password to be stored in the passsword vault: ").strip()
            if not new_pass.isalnum(): #checks if the entered username has spaces, or symbols or is a null input, which would be rejected and the program will loop back
                print("Your password for the website/app cannot be null, contain spaces or contain symbols \n")            
            elif len(new_pass) < 8: #the password must be at least 8 characters long to be accepted as valid
                print("Your new password must be at least 8 characters long: ")
            elif len(new_pass) > 20: #the password must not exceed 20 characters, otherwise it would be rejected and will loop back
                print("Your new password cannot be over 20 characters long: ")   
            else:
                validnewpass = False 
                passvault.append(new_pass) 

        validquit = True 
        while validquit:
            quit = input("\nDo you want to enter more websites/apps and passwords? Enter 'end' to exit or any key to continue to add more website/app names and passwords for them: \n> ")
            if quit in ["end", "End", "END"]: 
                return
            else:
                validquit = False 
                addapp() 
            return addapp        

def summary(): #The summary function is a print statement of how many password have been stored, the passwords with the longest or shortest characters are also displayed
    if len(passvault) > 0: #The user must have entered at least 1 password before the summary option can be viewed
            print("----------------------------------------------------------------------")
            print("Here is a summary of the passwords stored in the password vault:\n")
            print("The number of passwords stored so far:", len(passvault)) #len counts the amount of passwords stored in the passvault list
            print("Passwords with the longest characters: ", max(new_pass for (new_pass) in passvault)) #max finds the passwords appended in the passvault list with the longest password
            print("Passwords with the shortest charactrs: ", min(new_pass for (new_pass) in passvault)) #min finds the passwords appended in the passvault list with the shortet password
            print("----------------------------------------------------------------------")
    else:
        print("You have no passwords entered yet!")     

#Main routine
print("Welcome user to the password vault program")
print("In this program you will be able to store your usernames and passwords in password vaults and view them later on.\n")
validintro = False 
while not validintro:
    name = input(str("Greetings user, what is your name?: ")).lower().strip()
    if not re.match("^[a-z]*$", name):
        print("Your name must only contain letters from a-z: ")
    elif len(name) < 1: 
        print("Please enter a name that is valid: ")
    elif len(name) > 30:
        print("Please enter a name with no more than 30 characters long: ")
    else:
        validintro = True 
        print("Welcome to the password vault program {}.\n".format(name))

#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() 
        validintro = False

        if chosen_option in ["a", "A"]: 
            validintro = not login(username, password)

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

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

Answer 1

你有一个缩进错误。

您的 while keeplooping: 循环在 logged() 中只包含 try/except block ，因此它会一遍又一遍地循环。我想你想缩进它下面的 if 语句。

根据评论编辑:

当您 try/except 到达 except 时，它会打印语句然后继续。您没有在 except 语句中包含任何内容来告诉 while 循环重新开始。由于 modea 的分配失败，因此未分配它并在您尝试引用它时导致错误。如果您想在用户输入错误值时尝试其他输入，您可以使用 continue:

except ValueError:
        print("Please enter a valid option!")
        continue

这将导致整个指令字符串再次打印——可能有更好的逻辑，但至少可以防止错误。