While cannibalism is not common, it does happen. Yes multiple ball pythons can be housed together, but the average new owner has their hands full caring for a single snake in a single enclosure. Adding multiple snakes to a bigger enclosure only multiplies your problems and makes correct husbandry that much harder. I don't recommend anyone with less than 5-7 years of experience in snake keeping {and I don't mean keeping a single snake in an aquarium with no heat, no humidity and once monthly feedings} to even try housing more than one together.
Start out slow, learn all you can and make your first snake's enclosure as perfect as you can, then start with another snake in a separate enclosure and see how quickly you can get everything right. Once you can set up an enclosure just right on the first try, then you can try housing two of the same size in a single enclosure and see how things change and learn how to compensate. Truthfully, other than space concerns, there isn't much reason to house two or more together. And rack systems pretty much negate that issue. So in general you will find most people don't recommend it. The small gain is usually not worth the very real difficulties and hassles.
Gale