"It makes Python look like it's not a functional language. It perpetuates the idea that Python won't let you write elegant and stateless programs that behave in a functional manner."

I suggest Go for this use case. It's easy enough to read for this sort of thing even if you don't know the language, easy to link to running examples on the playground, and nobody will accuse you of showing Go off in a worse light than is called for because the Go equivalent of the imperative example shown really is the Go way to do it. Go is just about the most aggressively non-FP language out there today, making even Python look friendly to FP programming, despite the fact it has closures.