This is from the NERD website and pretty much says it all I think.
Enclosures can be as simple or elaborate as one is capable of caring for. Remember that the more "stuff" you put in a cage, the more "stuff" you have to clean & disinfect on a regular basis. That said, there are many different enclosures that work extremely well for ball pythons, including, but not limited to: plastic sweater boxes (i.e. Rubbermaid), melamine racks, Freedom Breeder cages, and any of the commercially available plastic-type reptile cages, (i.e. those from Vision Herp & other similar manufacturers). Glass aquariums & tanks are adequate; keep in mind that the screen tops on such enclosures can make it very difficult to maintain humidity levels. Also refer to our Snake Caging care sheet for more information. Juvenile ball pythons seem to do well in smaller enclosures that make them feel more secure; a small snake in a big cage can become overwhelmed & stressed. Fortunately adult ball pythons do not require exceptionally large or elaborate enclosures. A 36" x 18" x 12" enclosure will more than comfortably house an adult ball python. Remember that ALL enclosures must allow for a proper thermal gradient that the snake can utilize, with a hot spot on one end and a cooler spot on the other.
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Tosha 
1.1.0 Ball Python (Harry and Fluffy)
0.1.0 Siberian Husky (Kita)
0.2.0 Feline (Pippen and Pandora)
0.0.1 Dessert Tortoise (Pope)
5.4.2 Fish (1,2,3,4...)
0.0.1 Frog rescued from pool skimmer
0.0.2 Lizards rescued from pool skimmer