The only time I ever have this trick work is with flighty colubrid babies. I'll take one of those clear betta cups with the quarter sized holes in the lid, put a pinky in there with the little guy and let them slip back out through the lid when they're done.
The only reason it works is sometimes these little guys just get so worked up they hide everywhere when you try to show them the pinky. Once they have a minute to refocus they grab it and go no problems.
Ball pythons almost never act this way for me. So tricks like that aren't very likely to work.