Easiest way to grab one that's snippy is from the rear. Just grab a coil and pick it up. If most likely will calm down quickly once in hand. Look for tongue flicking and an extended body. These are your best signs of a a curious non aggressive BP. Also if you run a finger down the midline a relaxed snake's body will ripple. If they're tense, it'll feel solid and not react that way. No here's the scary part. If they don't relax and are still in the "S" position ready to tag you, ball them up. From the rear, come over the top of the head and force them to retreat into a more defensive posture. They're called Ball Pythons for a reason! A few times of this and they'll get that aggression is not acceptable. I've done this and it's worked well. I've actually been thinking about posting a video on this as I have a snippy candidate now. Let me know if you want to see it and I'll work on it tomorrow. I fed yesterday.
Dave