A lot depends on the composition of the tank, the locations of the openings for access, and what country you are in.

For PVC and/or other front access enclosures, radiant heat panels are the best solution for heating. This really only applies to the USA and Canada as we are the only ones who use these for reptiles and as such they are readily available to buy.

If you have a glass tank with a front opening, you can still use a radiant heat panel to heat the enclosure. For ball pythons it is also often advisable to heat one side of the floor with under tank heating unless you live in a climate that is warm enough for a BP most of the year.

More info on your tank and where you live can give insights on how to heat your enclosure.