From my website:
"An adult ball python will grow large enough that one adult mouse will not be a sufficient meal. Keeping this in mind, you should begin your ball python feeding on rats, which grow to be much larger than mice. This way, you won't have to struggle with switching your ball python from eating mice onto eating rats. Some ball pythons take a while to switch over, and some may refuse to switch over at all. So it is recommended that you begin feeding your ball python
rats from early on. If you stick to mice, you may end up feeding your adult ball python 3 or even 4 mice per feeding, whereas 1 rat could suffice. The cost of several mice might be more than one rat, so you should keep in mind what makes the most sense financially too."
My website.
I have a whole section dedicated to ball python feeding here:
Ball Python Feeding