Welcome to the site!
Yes, you need a longer enclosure than a higher enclosure. A 50 gallon would be good for an adult male or female.

Have you ever heard of using tubs for housing snakes? A 50 gallon would be pretty hard to keep temps and humidity up and tubs are cheap and easier to use than tanks. Unless you are good at keeping temps and humidity up in there.

If you decide to stay with a tank, click on the link in Cassandra's signature. You'll see her in the forums often. Lots of great info in that thread