let me guess the people at the pet store told you that it would be a good size for an adult python. Total bs, a full grown adult python can reach anywhere from 3-6 feet long. Even three feet 36 inches they would never be able to fully stretch out. I hate pet stores with a passion, anything to make a quick buck. Anyways I say build your own enclosure this way you can have it to your exact specs, and you can build to suit your ball python. If you are not good with tools and wood work there are always plenty of small time wood workers in the area who could build it for probaly about the same price you would have paid for that 30x12x15. Goodluck! and keep us updated on what you decide to do