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 name == username and password == userpassword:
        print("登录成功!")
        break
    else：
        if x != username
            print("用户名错误")
            continue
        if y != userpassword
           print("密码错误") 
    i -=1
    print("温馨提示:你还剩" + str(i) + "次机会")
    print("用户名和密码错误!请重新输入")
print("欢迎来到贝尔编程!")