1.py

i=3
username="python"
userpassword="123456"
while True:
    if i>0:
        i=i-1
        name=input("请输入用户名:")
        password =input("请输入密码:")
        if name == usernameand and password ==userpassword:
            print("登录成功")
            break
        elif name !=username:
            print("用户名不存在")
        else:
            print("密码输入有误，请重新输入！")
    else:
        print("你的登录以用完")
        exit()
print("欢迎来到贝尔编程")