Python：通过while循环调用函数

Question

我试图将我的程序扩展到一个程序，该程序将登录详细信息存储在字典中，当您尝试登录时，它应该询问您的用户名和密码，如果登录详细信息与附加到字典中的信息相匹配，它会显示“您已登录！”，但我似乎无法调用我的login（）函数，除非在没有输入登录信息时打印出else print语句但是它并没有循环回到菜单（），就像我把它放在while循环中一样。我想我有点在主程序中搞砸了我的while循环，但似乎无法让我的脑袋绕过它。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

这是因为在打印之后，“你没有用户名和密码存储！”，你回返回外，同时却从未validintro更改为false。这会导致while循环结束。

您应该从登录返回一个值，以知道是否没有用户，并检查在while或login函数中，在else部分中设置全局validintro为false（我会推荐第一种方法）