I recommend without reservation the cages made at Reptile Basics. Here's a link to the 3x2x1 cage that will house a ball python for their lifetime: http://www.reptilebasics.com/2x3-Cag...h-p-16286.html.

I have 6 of these cages and love them for their ease in maintaining temps and humidity as well as their ease of cleaning. Also, due to the drop-down door, a snake could never escape unless the keeper forgot to latch all three latches!!