'ratsnakes' is an immense term covering species from Central and North America, Asia, and Europe so you'll have to give us some kind of clue what you're after.
If you want an 'easy' ratsnake that you can keep like a corn, then you're best looking at the North American rats so do a google on these:
I used to have a yellow rat snake. 5ft 6ins long and very very feisty. Would tag you for no reason. Very active and not always happy to be handled. He was captive bred but was more than a little wild. Do some research, infact do a lot of research coz its not like keeping a cornsnake and if you get a feisty one it might put you off!! They are quite shy most of the time and like to hide away.......widey
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