編寫login.py腳本，實現以下目標：

1. 支持新用戶註冊，新用戶名和密碼註冊到字典中
2. 支持老用戶登陸，用戶名和密碼正確提示登陸成功
3. 主程序通過循環詢問進行何種操作，根據用戶的選擇，執行註冊或是登陸操作

   #!/usr/local/bin/python3
   # -*- conding : utf-8 -*-
   """
   @Time         :  19-3-16 上午10:45
   @Author       :  xq
   @Software     :  PyCharm
   @File         :  userlogin.py
   @Description   :
   """
   import
    
    getpass
   
   userdb = {}
   
   def register():
       username = input(‘item to username: ‘).strip()
       if username not in userdb:
           password = input(‘item to userpasswd: ‘).strip()
           userdb[username] = password     #key不在字典就添加
       else:
           print(‘%s already exitsts!!‘% username)
   
   
   
    
   def login():
       username = input(‘username: ‘)
       password = getpass.getpass(‘password: ‘)
       # if username in userdb and userdb[username] == password:
       # if userdb.get(username) == password:
       if userdb[username] == password:          #判斷鍵值等不等
           print(‘Login successful‘)
       else
    
   :
           print(‘login failed‘)
   
   
   
   
   def show_menu():
       prompt = """(0)register
   (1)login
   (2)quit
   please choices(0/1/2) : """
       while True:
           cmd = {‘0‘: register,‘1‘: login}
           choice = input(prompt).strip()  # 去除用戶輸入的兩端的空白字符
           if choice not in [‘0‘,‘1‘,‘2‘]:
               print("Invalid input,please try again")
               continue
           if choice == ‘2‘:
               break
           cmd[choice]()
   
   if __name__ == "__main__":
       show_menu()

模擬用戶登陸註冊