Ball Pythons are not very active so a small enclosure is fine. Use a 10-20 gallon tank for younger snakes, a 30 or 40 gallon tank for an adult. Just remember to make it secure because if there is a way to escape, they will.
Feeding: Ball pythons can be fed rats or mice. Some use frozen/thawed or live. Be careful with larger live prey that they do not harm your snake. You can feed your snake every 5 days out to once every other week. Some ball pythons go months without eating. You can move your snake to a separate enclosure for eating to continue the taming process. As long as body weight and condition are maintained, this is not problematic. If your snake stops eating, carefully examine the handling, health, and environment of the snake to make sure stress isn't the culprit. Consult a knowledgeable vet or experienced keeper for help if the fast is prolonged or causing weight loss. If necessary, some tricks to entice a python to eat include dipping the prey in chicken broth, trying different colors of mice or rats, exposing the brain of the prey before feeding it, feeding at night, covering the cage with towels after offering a mouse. You may even want to try feeding a hamster or gerbil, although this may make your snake more likely to refuse mice if it develops a preference for hamsters and gerbils.
*Gerbils cannot be used in the state of California