Add python and node virtualenvs

python_environment/default.nix

@@ -0,0 +1,20 @@
+with import <nixpkgs> {};
+
+stdenv.mkDerivation {
+  name = "myPythonEnv";
+  buildInputs = with pkgs; [
+    python36Full
+    python36Packages.virtualenv
+    python36Packages.pip
+  ];
+  src = null;
+  shellHook = ''
+    # set SOURCE_DATE_EPOCH so that we can use python wheels
+    SOURCE_DATE_EPOCH=$(date +%s)
+    virtualenv --no-setuptools venv
+    export PATH=$PWD/venv/bin:$PATH
+    if [ -s requirements.txt ]; then
+      pip install -r requirements.txt
+    fi
+  '';
+}