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You need to set your photobucket to public, right now it's set to private and we can't see the pictures. Then use the "IMG" code on photobucket to post pictures here.
You have a normal type ball python.
Without knowing when he hatched it is impossible to know for sure. BP's can grow at very different rates depending on care and how much food is offered.
Don't bother trying to measure length, it really is a waste of time. Most people weigh their snakes to track growth. A good kitchen scale that measures in grams is best.