Ball pythons, always in their own cage. They're just too insecure. You may get a few individuals who will accept being fed outside their cages, but I seriously doubt it's that common.

I only see my ball pythons coming out looking for food on or the day just before feeding day. A little nudge with a hook or a squirt from a spray bottle, and they settle down. Cage aggression is virtually never an issue, and it's easily defused if it occurs.

Regarding the Anaconda--it's a double-edged sword. Yes, your anaconda may never see its cage as being the place where it is fed. However, you will wind up having to move a keyed-up anaconda that has just been fed and may be looking for seconds, back into its enclosure. Good luck with that, and make sure your insurance is paid up.