Well one way of going about it is a hybrid solution. So you set up your python dev directory with a nix file, but then you use pyenv or whatever to encapsulate

Well one way of going about it is a hybrid solution. So you set up your python dev directory with a nix file, but then you use pyenv or whatever to encapsulate everything else inside it using python tooling. So it's not strictly Nix-all-the-way-down, but at least as far as being in the directory is concerned, the "right" python version and libraries are available.