Well you have to pop the hole, and if there is nothing that pops out, its a girl, otherwise you have a boy. Just to tell you though, not sure of the temperament of your ball python,not all snakes like this being done. read more
The male snake has a hemipenis, which is like a fork tongue. You can tell by probing the snake (wouldn't recomend, if you've never done this before) otherwise call a pet store who are good with snakes and take it in and they will be able to tell you. For free! instead of paying at a vet. read more
Unless you plan on breeding them, there's no reason to, just pick a gender to call it. If you really need to know, there are several methods. read more