I think something like Flask is super easy to learn. Go one step further and use Bottle, its a single Python file and its API is one page long. Its basic, but

I think something like Flask is super easy to learn. Go one step further and use Bottle, its a single Python file and its API is one page long. Its basic, but that should be the point. You can fluidly graduate from Bottle to Flask + extensions or to Django depending on which you prefer. Or just start in Flask - the base API is pretty much the same, its just it has a ton of extensions to implement all the server functionality you could want.