Hi,
Im basically going to repeat what others have said.
1. Your snake is defensive not aggressive. Is there anything you are doing or anything in their environment causing the snake stress? Loud music, lights on at night, is the tank in a place with a lot of traffic? Try moving the snake to a quite room where they will feel secure. Is the heat and humidity correct.
2. You need to approach the snake with more confidence. If you are nervous or jerking your hand so you don't get bit, the snake may sense this odd behaviour.
3. Someone mentioned placing the snake on your lap and covering with a towel. This is a good idea. Try to get the snake out calmly using a hook and try this. Once a week is enough to begin with and gradually increase handling.
4. People have mentioned problems with the food you are feeding. I don't think they can accurately assume this without knowing the weight and girth of the snake (maybe i missed this). Feeding an appropriately sized mouse/rat every 7-10 days is best.
For more information check out: http://www.reptilerange.com/ball-python-care-sheet/
Any questions on the above, I will be happy to answer.
Liam.