If you haven't done so already, I would suggest a complete substrate change. The reason I say this is that if your ball python had a bad shed, there may be some small pieces of shed in your substrate. Why does that matter you ask? I don't know why ants love shed snake skin so much, but I have noticed that sometimes when I have to aid a snake with a bad shed, I will do it right outside of the snake building, and alot of pieces of shed will hit the ground. By the time I go back inside and put the snake up, and mess around with some other stuff in the snake room, say thirty minutes, and come back outside, the pieces of shed are covered with ants. Anyway, it was just a thought, and may not resolve your problem, but it may just help.