move default.nix to shell.nix

node_environment/shell.nix

@@ -1,11 +1,9 @@
-with import <nixpkgs> {};
-
-stdenv.mkDerivation {
-  name = "myNodeEnv";
+{ pkgs ? import <nixpkgs> {} }:
+pkgs.mkShell {
+  name = "node-environment";
   buildInputs = with pkgs; [
     nodejs
   ];
-  src = null;
   shellHook = ''
     mkdir -p .npm
     if [ -s global_packages.txt ]; then

python_environment/shell.nix

@@ -1,12 +1,10 @@
-with import <nixpkgs> {};
-
-stdenv.mkDerivation {
-  name = "myPythonEnv";
+{ pkgs ? import <nixpkgs> {} }:
+pkgs.mkShell {
+  name = "python-environment";
   buildInputs = with pkgs; [
-    python3Full
+    python3
     python3Packages.virtualenv
   ];
-  src = null;
   shellHook = ''
     if [ ! -d .venv ]; then
       python -m venv .venv