Add separate python venv template

templates/python.nix

@@ -17,8 +17,5 @@ pkgs.mkShell {
 
   shellHook = ''
     export LD_LIBRARY_PATH="${pkgs.zlib}/lib:${pkgs.libgccjit}/lib"
-    python -m venv .venv
-    source .venv/bin/activate
-    pip list --outdated | grep -iE "^(pip|wheel)" > /dev/null && python -m pip install --upgrade pip wheel
   '';
 }

templates/venv.nix

@@ -0,0 +1,24 @@
+{ pkgs ? import <nixpkgs> {}, python ? pkgs.python39, ... }:
+
+let
+  python-packages = ps: with ps; [
+    pip
+    setuptools
+    wheel
+  ];
+in
+pkgs.mkShell {
+  nativeBuildInputs = with pkgs; [
+    (python.withPackages python-packages)
+    git
+    zlib
+    libgccjit
+  ];
+
+  shellHook = ''
+    export LD_LIBRARY_PATH="${pkgs.zlib}/lib:${pkgs.libgccjit}/lib"
+    python -m venv .venv
+    source .venv/bin/activate
+    pip list --outdated | grep -iE "^(pip|wheel)" > /dev/null && python -m pip install --upgrade pip wheel
+  '';
+}