Poetry2Nix Development Flake with Matplotlib GTK Support

Posted on 11.05.2024 17:57 in Hacks • 355 words • 2 minute read

I recently had the pleasure to dive back into python for work. In the past, I was happily using org-babel notebooks through emacs-jupyter. However, I have since switched to a more REPL/script driven workflow as I find that programming notebooks require a great deal of discipline to not end up as a horrible mess. For my new workflow, I need interactive plotting to work.

So let’s get straight to the meat. The following Flake dives you a development shell that tries to replicate the underlying poetry project in full nix using poetry2nix.

{
  description = "[your description]";

  inputs = {
    flake-utils.url = "github:numtide/flake-utils";
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable-small";
    poetry2nix = {
      url = "github:nix-community/poetry2nix";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };

  outputs = inputs @ { self, nixpkgs, flake-utils, ... }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = nixpkgs.legacyPackages.${system};
        poetry2nix = inputs.poetry2nix.lib.mkPoetry2Nix { inherit pkgs; };
      in
      {
        packages = {
          yourPackage = poetry2nix.mkPoetryApplication {
            projectDir = self;

            # set this to true to use premade wheels rather than the source
            preferWheels = false;

            # this enables interactive plotting support with GTK
            overrides = poetry2nix.overrides.withDefaults (final: prev: {
              matplotlib = with pkgs; prev.matplotlib.override
                {
                  passthru.args.enableGtk3 = true;
                };
            });
          };
          default = self.packages.${system}.yourPackage;
        };

        # Shell for app dependencies.
        #
        #     nix develop
        #
        # Use this shell for developing your app.
        devShells.default = pkgs.mkShell {
          inputsFrom = [ self.packages.${system}.yourPackage ];
          package = with pkgs; [
            # any development dependencies that you might have in nixpkgs
            ruff
            pyright
          ];
        };

        # Shell for poetry.
        #
        #     nix develop .#poetry
        #
        # Use this shell for changes to pyproject.toml and poetry.lock.
        devShells.poetry = pkgs.mkShell {
          packages = [ pkgs.poetry ];
        };
      });
}

The workflow is as follows. Running nix develop .#poetry will give you a shell with poetry available. You can then poetry init and poetry add and poetry lock (not install) to your hearts content. A plain nix develop will then set up the environment according to the poetry.lock that poetry generates. Note that this pull request has to be resolved before the above works with preferWheels = true.

You might want to checkout direnv and nix-direnv for added convenience.