add flake

flake.nix

@@ -0,0 +1,27 @@
+{
+  description = "Python development environment";
+  inputs.nixpkgs.url = "nixpkgs/nixos-unstable";
+  outputs = { nixpkgs, ... }: let
+    system = "x86_64-linux";
+    pkgs = import nixpkgs {
+      inherit system;
+      config.allowUnfree = true;
+    };
+  in {
+    devShells."${system}".default = pkgs.mkShell {
+      packages = with pkgs; [
+        (python312.withPackages (
+          ppkgs: [
+            python312Packages.django
+          ]
+        ))
+        # other packages
+      ];
+
+      shellHook = ''
+        echo "Welcome to your declarative Python development environment!"
+        python --version
+      '';
+    };
+  };
+}