diy2.py

i=3
username = "python"
userpassword = "123456"
while True:
    if i>0:
        name = input("请输入用户名:")
        if name!=username:
            print("用户名错")
            i=i-1
            continue
        password = input("请输入密码:")
        if password!=userpassword:
            print("密码错误")
            i=-1
            continue
        if name == username and password == userpassword:
            print("登录成功!")
            break
        else:
            print("用户名密码错误重输")
            i=i-1
    print("限制")
    exit()
print("欢迎")