Ball pythons are one of the least active species of snakes you could own so it probably hasn't gone very far and there's a very good chance that he is within a few yards of his enclosure. Search at night, look in sofa cushions, closets, and also look on/around appliances which give off heat...refrigerator, oven, water heater, vcr, tv etc. Remember, pythons do not see like we do, they see through infrared vision which is basically heat vision so it'll probably head somewhere where it can get warm.
As you probably know balls tend to hide and curl up real tight when they are stressed so look in small, dark, cramped but warm spaces...anywhere near a heat source is a place to start (if there are any places to bask in sunlight that's also likely).
As ball pythons can aestivate (go in to a state of dormancy/hibernation) they can go for months without eating so you don't need to worry about your snake starving. And if its any consolation ball pythons have been known to turn up in empty tumble dryers or under sofas up to 5 or 6 months after they escape!
Best of luck