What size enclosure do you have?
An adult Ball Python will top out around 4-5 feet, and weigh around 5 lbs (this varies by snake and gender, males tend to stay much smaller than females)
BP's are good at escaping, but as long as you secure your cage you have nothing to worry about. On glass tanks I place a brick on all 4 corrners of the screen top. This makes it impossible for a full grown BP to escape, it's just that simple.
A BP has never been associated with the death of a human, not even a baby. They simply don't get big enough or strong enough do do any real harm. Even the largest BP couldn't eat a cat or small dog, and in fact the opposite is more likely to happen, the cat/dog if much more of a threat to the BP.
You might want to look into getting a professionally made reptile cage. I use cages made by Animal Plastics. They are made from 1/2" thick plastic with sliding glass doors on the front. You can get them with a lock for the doors to ensure that the snake can't get out, and other people can't get in.
Here is their website (I recommend the T8)
http://www.apcages.com
And here is a thread that covers these cages in detail:
http://ball-pythons.net/forums/showt...With-Pictures!