When I first got my ball python from the store, they had two in stock. I ended up getting the 'mean' one (or so they said) because of his size and because he is a fierce eater. I had his cage set up and heated, so when I got back to my apartment, he could hide and get used to his surroundings. So far, he has yet to strike at me. Because they had him pegged as the mean one (the employee even pulled down her long sleeve shirt in case he bit her), I made sure to monitor how I handled him. This includes:
-making sure the temps and humidity are in range
-not moving my hand in front of his face when I pick him up
-not handling him too often (even though its tempting!)
Good luck though. On the bright side, having bite marks on your hands and arms can make you look pretty hardcore.