While client side and server side validation aren't necessarily the same code, the fact that it's the same language makes it possible. If you have JS on the cli

While client side and server side validation aren't necessarily the same code, the fact that it's the same language makes it possible. If you have JS on the client and Python on the server you will have to write validation code twice regardless. So no, it's not a given that you will avoid duplication but possible trumps impossible.