Python编程的新手，有人可以解释这个程序的错误吗？

I am very new to Python programming, I am writing a simple fighting game at the moment (text based) that is extremely simple as I'm just learning the basics at the moment. I have placed the code for my game below (it is not finished), my problem is that every time I run the program, when you enter which character you'd like to play as this error occurs.I am very new to Python programming, I am writi