For an adult you need a minimum of 3 feet long by 15 inches to 2 feet wide. Ideally a 4 foot by 2 foot enclosure is what you want.

Height is not as important but they do like to climb slightly so the closer to 2 feet high, the better. Most PVC enclosures are around 15-18 inches high. Too high and heating can start to be a concern.

Theoretically a ball python will use as much as you can provide but heating becomes more of a challenge the larger you get or make.

This is just my opinion so it is not gospel but a T10 enclosure from animal plastics is the ideal dimensions for an adult.