While most of my ball pythons are typical laid back balls I've had a few feisty ones over the years.
I had a het albino male that would strike for a while when I first got him at about a year old. Two of his 4 daughters would also strike when young and hissed up to about 2 years old. One of his grandsons by one of the hissy daughters was a constant striker for the few months I had him but his sister was fine. I'm starting to think that in my case it was some sort of dominant aggression gene.
I currently have a small adult (1,800 grams) pet store girl that regularly strikes at me. Unfortunately the male that I need to pair her with is one of those rigid (scared) balls and also bit me a while back although he hasn’t been particularly aggressive most of his life. I'm thinking mean kids from this pair but hopefully will get a nice one or two out to hold for breeders (I’m only breeding them for a morph project).
Sometimes I think breeders have selected for mean ball pythons as you hear more about them in certain morphs (piebald especially). The general belief seems to be that they will be better feeders. There might well be a correlation between aggression and feeding response but I know I've worked with fabulous feeders that where not aggressive so I would hate to see ball pythons loose their reputation as trustworthy snakes due to excessive selection for aggressive lines.