IF the animals you buy ARE 100% hets, then when bred together het X het (and the hets are the same gene), ON AVERAGE 1/4 will be that gene. For example, if you breed het albino X het albino, 1/4 should be albinos. This is a statistical average and sometimes you can get more and sometimes less.
With ball pythons, I would pay the extra money to get them from a VERY reputable breeder. There are a lot of low life people out there that will sell normal ball pythons as 100% hets and when you breed them years down the road you will get only normals.
Good luck....