What Davebear said.
Aside from frequent, careful, and gentle handling, you don’t really train snakes. Boas in general are fairly mellow snakes, especially red-tailed boas. I’ve got a Brazilian rainbow boa who is a bit cranky, but so cranky as the majority of pythons I’ve met.
If you’re just considering a snake and not necessarily a boa, there are other, smaller, very flashy looking snakes that take less room, less food, and less bodily strength to handle. Most boid species are fairly largeish, but there are quite a few smaller colubrids such as cornsnakes, kingsnakes, and milksnakes that are quite lovely and not so big.
As for my own zoo, at the moment I’m down to four snakes, and a rat, although at one point, I had a pack of flying geckos, a gopher snake, and a very large saltwater tank. The snakes I’ve got are amelanistic cornsnakes (Ruby and Ziti), an anerythristic cornsnake (Eve), and the brazilian rainbow boa (Ziggy Stardust, aka David Boa.
). The rodent posse used to number in the double digits, but alas they have slowly been getting very old and going off to the big Cheereo box in the sky, and now I’m down to one nekkid rat, named Robert Ratchenburg. It’s killing me that he’s by himself, as rats are such highly social little critters, but I’ve grown tired of going through traumatic pet deaths so often–and I think I’m going to stick with critters with a bit longer lifespan.
Make no mistake, though, rats are far and away the best small animal pets available. They’re very bright, friendly, tidy little critters. Mine knew their names and would come running when I called them. I’d leave the door to their cage open when I was home and they’d run around and cause chaos, but were never really destructive at all. I bred fancy rats for quite a while, mostly blues, tailless, and rexes.
Currently, Mr. Armadillo and I live in Northern California, where practically everything is illegal to keep as a pet. However, we are moving to Oregon in the Fall, at which point I will be getting a pet skunk 
Peace,
~mixie