day1 if 判断

_username = "mask" _password = "a111" username = input("username:") password = input("password:") 
 if _username == username and _password == password: #若是 _username 等于username 而且 _password 等于 password 执行下面缩进代码 print('Hello {name}'.format(name=username)) else: #不然执行下面的缩进代码 print('Invalid username or password !')