Ball pythons might grow a foot a year at first but they slow way way down after that.
800 grams is a good weight gain for a male that is 1 year old but you'll see after he gets a little bigger his growth will start to slow down dramatically.

This boy is a big boy, he's a 9 years old clown, around 2200 grams and about 4 1/2 feet.
Big males are excellent breeders and make for fun pets.