用户登录（简易版）

#一、简易版用户登录，此程序直到用户输入正确的用户名和密码，不然不会退出
 1 _name = "liangchen"
 2 _passwd = "abc123"
 3 while True:
 4     username = input("username:")
 5     password = input("password:")
 6     if username == _name and password == _passwd:
 7         print("welcome %s login"%_name)
 8         break
 9     else:
10         print("Invalid username or password!")

#二、简易版用户登录，用户输入正确的用户名和密码或者用户输入三次错误都会退出登录
_name = "liangchen"
_passwd = "abc123"
login_time = 0
while login_time<3:
    username = input("username:")
    password = input("password:")
    if username == _name and password == _passwd:
        print("welcome %s login"%_name)
        break
    else:
        print("Invalid username or password!")
    login_time += 1
    if(login_time == 3):
        print("输入次数过多，退出登录！")
        break