diy4.py

username="python"
userpassword="123456"
while True:
    name=input("用户名：")
    password=input("密码：")
    if username==name and userpassword==password:
        print("登录成功")
        break
    if username!=name:
        print("用户名错误！请重新输入！")
        continue
    if userpassword!=password:
        print("密码错误！请重新输入！")
print("欢迎来到贝尔编程")