I would not use sand for ball pythons. Cypress mulch, aspen shavings, and newsprint will be the most widely used in tubs/enclosures. The first two most commonly used because they do wonders on holding humidity, and paper because of the ease of cleaning.

Sand really does not retain heat as well as you may think. You don't have to worry about them ingesting aspen/cypress, if you think about it they have to digest mouse/rat hair and bones whats a little wood in the mix?

Jason