Due to electrical short risks, and overheating, the human heat pad should be beneath the cage. The one you buy from a walmart or a CVS has three settings. Use it on the lowest setting. If the temp in the room is in the 70's, that should bring the heat to a little under 90 directly over the heat pad. Measure the temperature on the heat pad itself, as well as on top of the glass it sits beneath. If it is still getting to warm, you can put a rheostat (or a lamp dimmer from a hardware store, basically the same thing) in line between the pad and the outlet. As a general rule, it is far better to err on the cool side than the warm, but sustained exposure to low temperatures will eventually result in a host of health problems including prolapsed intestines (inability to digest, resulting in a big mess) increased liklihood of respiratory infections, etc. Too much heat, however, can kill in a few short hours, or, if not fatal, can result in permanent neurological problems. Get a dual probe thermometer ($15 or less at self-same retail outlets) and keep good track of the both the cool side and the warm side. Stick on aquariam thermometers are nearly useless, as your snake will never be suspended along one side of the wall.
Good luck and I hope you have a lot of fun with it...in the next couple of months you will get the environment down pat, and spotted pythons are pretty hardy, so don't worry too much.
