Thank you everyone!
My Boyfriend just got a Ball Python (Cherry) and wanted a more natural looking substrate for her, he found it hard to get facts and not a bias opinion about it but the snake "expert" at the pet store told him the only type you can ever be use for pythons is Aspen, I found this hard to believe so I started searching for options and found this site and posts.

It seams to me there are lots of options for substrate, and it comes down to personal choice and for you to take what ever precautions you can (just like any other pet) so we will try out different types until we find what works best for our selves. Thanks again