Installing packages from nixpkgs

In some cases a package isn't published on PyPI, but is packaged in nixpkgs, or you might be struggling trying to figure out the overrides to build a particular package. In such cases it's possible to use Python packages from nixpkgs through an interoperability layer.

We are using the seccomp package for demonstration here, which is not available on PyPI.

Installing a wheel (recommended)

By using UV_FIND_LINKS and a shellHook we can install the nixpkgs built wheel, making it possible to use both impure (uv managed) workflows & pure uv2nix managed workflows.

let
  python = pkgs.python3;

  uv-links = pkgs.symlinkJoin {
    name = "uv-links";
    paths = [
      # Note: Using the dist output which contains a wheel
      python.pkgs.seccomp.dist
    ];
  };

in
mkShell {
  packages = [ pkgs.uv python ];
  shellHook = ''
    ln -sfn ${uv-links} .uv-links
    export UV_FIND_LINKS=$(realpath -s .uv-links)
  '';
}

To be able to read the sources from a Flake evaluation you will also have to override the seccomp package sources, as .uv-links is not added to Git.

let
  pyprojectOverrides = final: prev: {
    seccomp = prev.seccomp.overrideAttrs(old: {
      buildInputs = (old.buildInputs or []) ++ python.pkgs.seccomp.buildInputs;
      src = python.pkgs.seccomp.dist;
    });
  };
in ...

Using pyproject.nix hacks

It's also possible to skip making uv aware of the package and only add the nixpkgs package from a Nix evaluation.

let
  pyprojectOverrides = final: prev: {
    seccomp = hacks.nixpkgsPrebuilt {
      from = python.pkgs.seccomp;
    };
  };

  pythonSet' = pythonSet.overrideScope pyprojectOverrides;
in
  pythonSet.mkVirtualEnv "seccomp-env" {
    seccomp = [ ];
  }