Nix flake with cuda enabled pytorch

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1

Hello,
I’m new to nix and I’m trying to set up a pytorch development environment using a nix flake. Here’s the flake:

{
  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs/24.05";
    flake-utils.url = "github:numtide/flake-utils";
  };

  outputs = { self, nixpkgs, flake-utils }: 
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = import nixpkgs {
          inherit system;
        };
      in {
        devShell = with pkgs; mkShell {
          packages = [
            python310
          ];
          
          env = {
            LD_LIBRARY_PATH = pkgs.lib.makeLibraryPath [ pkgs.stdenv.cc.cc ];
          };
        };
      }
    );
}

And the following is my requirements.txt:

--extra-index-url https://download.pytorch.org/whl/cu121
torch==2.5.1+cu121
numpy

When enter the dev shell and create (via python3 -m venv .venv) and activate venv and install the packages from the requirements file and test for cuda support (via torch.cuda.is_available()), the test returns False. However, if i don’t enter the dev shell (basically not use the flake) and set everything up via system’s python, cuda is available.

Before using requirements.txt I tried with poetry and poetry2nix, and ran into the same issue. I’m not entirely sure whats going on here. Am I missing something?