diy2.py

i=3
username = "python"
userpassword = "123456"
while True:
    if i>0:        
        myusername = input("请输入用户名:")
        password = input("请输入密码:")
        i -= 1 
        if myusername == username and password == userpassword:
            print("登录成功!")
            break
        if myusername != username:
            print("用户名错误!请重新输入")
        if password != userpassword:
            print("密码错误!请重新输入")
    else:
            print("登录次数已用完")
            exit()
print("欢迎来到贝尔编程!")