Corn snake, totally. They get pretty long but they're not that thick. Can get up to 6 feet but all the adults i've seen have been MAYBE 4. They're VERY docile. Babies can be snippy but they barely even have teeth, and once they're a few months old they'll calm down. Love to be handled, don't need complicated lights, just an under-tank heating pad. I started out with my two babies in a 10 gallon and moved them up to a 30 gallon at almost a year. Don't need a ton of room as they're docile in the tank, as long as you take them out some.
Mine both have eaten frozen no problem. They're easy pets and some of the most fun, gentle creatures i've ever met. Lol, i watch TV and stuff with mine all the time.