Yes, you can... kind of... train a ball python. Two of my girls are conditioned to know that three taps on the wall of their tub means they're about to get fed. They come out from under the paper towels, look towards the noise and get ready to strike. I've been doing this for months with them. I've also noticed that those two have never missed a meal, though that could just be coincidence.

I tried the chicken soup thing. Didn't work for me. And just saying, but how does chicken soup even make sense? I mean... ball pythons don't eat chickens, so how does this trick translate into the python deciding to eat?