diy2.py

i=0
username = "python"
userpassword = "123456"
while True:
    name = input("请输入用户名:")
    password = input("请输入密码:")
    if name != username 
        print("用户名错误!请重新输入")
        if i==3
            exit()
        else 
            i=i+1
        continue
    if password != userpassword
        print("密码错误!请重新输入")
        if i==3
            exit()
        else 
            i=i+1
        continue
    print("登录成功!")
    break
print("欢迎来到贝尔编程!")