da.py

username = "python"
userpassword = "123456"
i=3
while True:
    if i>0:
        name = input("请输入用户名:")
        password = input("请输入密码:")
        i -= 1
        if name == username and password == userpassword:
            print("登录成功!")
            break
        if name != username:
            print("用户名错误")
            continue
        if password != userpassword:
            print("密码错误")
        print("用户名和密码错误!请重新输入")
    else:
        print("你的账号已被锁定，请携带身份证来我司解锁")
        exit()
print("欢迎来到贝尔编程!")