It's good that you're asking questions! Ball pythons aren't basking animals (like bearded dragons - just think of how much time BP's spend hiding), so generally a heat lamp on its own isn't enough. They need belly heat to digest, hence the UTH recommendation. But UTH's can get waaay too hot if they aren't regulated in some way, which is why they need a thermostat to control the temperature, very similar to how a thermostat in your house keeps a specific temperature by turning the air or heat on/off.
In addition to belly heat, ball pythons need a thermal gradient so they can choose to either warm up or cool down at different points in their tanks. UTH's don't really heat the air (otherwise known as ambient temperature), just the ground. So depending on how warm the room is where the cage is, you might need a heat lamp or a ceramic heat emitter in addition to a UTH.
As an example, we use UTH's and infrared bulbs. The UTH is hooked up to a thermostat to provide a hotspot of 88 to 90 degrees under the hot hide, whereas the heat lamp is hooked up to a dimmer to provide an ambient temperature of 80 degrees in the enclosure. We had to play around with the settings on both to get the temperatures right, and we spot check temperatures with a temp gun. We also have a thermometer/hygrometer in each cage to monitor humidity and ambient air temperature.
There are other ways to heat cages as well, including heat tape, Flexwatt, and radiant heat panels. we are planning to upgrade our glass aquariums to PVC enclosures, and when we do, those will be heated by only radiant heat panels unless we need the extra oomph heat tape provides.
Hopefully this helps! You've come to a great place to learn about BP's.
