nixos/templates/venv.nix

{
  pkgs ? import <nixpkgs> {},
  python ? pkgs.python39,
  ...
}:
pkgs.mkShell {
  nativeBuildInputs = with pkgs; [(python.withPackages (ps: with ps; [pip wheel])) poetry git];
  shellHook = ''
    [ -d .venv ] || python -m venv .venv
    source .venv/bin/activate
  '';
}