Despite ball pythons being nocturnal, they do wake up throughout the day, so suggesting that the two species won't see each other due to sleep patterns is not correct. Also, if you were sleeping in a nice comfy bed and some other person was cruising over you while you were trying to sleep and moving all around your house, you'd wake up too. While ball pythons mainly eat rodents, I'm not certain a hungry ball wouldn't eat (or attempt to eat) a smaller snake, not to mention different heating and humidity needs. All and all, each species should be kept in cage set up for its own specific needs.
