dotnet: version 9 + added python *especially py2cfg for static analysis)

dotnet.nix

@@ -4,7 +4,7 @@ let
   # Rolling updates, not deterministic.
   pkgs = import (fetchTarball "channel:nixpkgs-unstable") { };
 in pkgs.mkShell {
-  buildInputs = [ pkgs.dotnet-sdk ];
+  buildInputs = [ pkgs.dotnet-sdk_9 ];
   shellHook = ''
     exec zsh
   '';

python.nix

@@ -0,0 +1,8 @@
+let pkgs = import (fetchTarball "channel:nixpkgs-unstable") { };
+in pkgs.mkShell {
+  packages =
+    [ (pkgs.python3.withPackages (python-pkgs: [ python-pkgs.py2cfg ])) ];
+  shellHook = ''
+    exec zsh
+  '';
+}