diy2.py

i=3

username = "python"
userpassword = "123456"
while True:
    if i>0:
        i-=1
        name = input("请输入用户名:")
        password = input("请输入密码:")
        elif name == username and password == userpassword:
            print("登录成功!")
            break
        elif name!=username:
            print("用户名不存在")       
        elif password!=userpassword:
            print("密码错误")
    else:
        print("已经被锁定")
        exit()
print("欢迎来到贝尔编程!")