Most Ball PYthons available today are captive bred or captive born. Ball pythons used to have a bad reputation for not feeding well in captivity because most were wild caught adults that would never adjust. Luckily they are so popular that babies are readily available. 

A few common problems in regards to non feeding ball pythons-

Babies - some may feel insecure in a large enclosure with to much open space. A dark hide spot, and a smaller darker cage may be all that is needed to stimulate feeding.

Baby ball pythons that have eaten before, and now do not after you take it home, may also be use to a certain food item. Always ask what it was feeding on when you purchase! Even color of mouse or rat is important. Some snakes are used to mice so won't eat rats till later in life. Others only eat black mice but not white, and vice versa. 

Temperature is also crucial. A cold snake knows not to eat, and if it does, it may throw up. Always provide a cool hide and a warm hide so the ball python can choose what temperature it likes. Just because you have a heating pad does not mean the snake is warm enough. The air temperature in the cage may be too low, and this could lead to feeding problems or even respiratory problems. A small wattage bulb may be needed to keep the air temperature warm as well. 

Adults- a lot of adult ball pythons are set in their ways. If they have been eating white rats their whole lives, they may not eat colored rats. 

Alot of adult male ball pythons stop eating in the fall all the way to spring. It's is normal as long as the snake doesn't loose more then 10% body weight. They are in breeding mode, and some eat and some do not. 

If you purchased a snake that was raised in a rack system and place it in a glass tank with open spaces, it may not adjust. You may need to make it feel more secure by using a large Tupperware system to keep the snake or providing more hide spots. 

Some females if bred, or cycling may not feed either. As long as they don't loose to much weight, they should be fine. 

A ball pythons that has eaten rats and stops feeding but shows interest, may need to get stimulated by something new. A mouse usually does the trick for 2-3 feedings, and then sometimes they will resume feeding on rats. 

The size of the meal is important as well. A shy snake may shy away from a medium rat but will readily eat rat pups. 

If you experience a drastic drop in weight, and other clinical signs of being sick such as wheezing, coughing, or drool, you need to see a vet ASAP!

Ball pythons experience fasting periods occasionally, and it is completely normal. Some ball pythons are on a clock and every year for 2-3 months just won't eat. Monitor their weight, and health, and most should be fine as it is natural for them.