diy2.py

username = "python"
userpassword = "123456"
i=3
while True:
        name = input("请输入用户名:")
        password = input("请输入密码:")
        if i > 0
            i-=1
        if name == username and password == userpassword:
            print("登录成功!")
            break
        elif name != username:
            print("用户名错误")
        elif password != userpassword:
            print("密码错误")
        else:
            print("账户已锁定")
            exit()
        print("用户名和密码错误!请重新输入")
    print("欢迎来到贝尔编程!")