nix flake init --template "https://flakehub.com/f/the-nix-way/dev-templates/*#python"

Author: berquist

.envrc

@@ -0,0 +1 @@
+use flake

.gitignore

@@ -1,5 +1,7 @@
 *.pyc
+.direnv
 .idea
+.venv
 
 regressionfiles.diff
 regressionfiles.yaml.orig

flake.lock

@@ -0,0 +1,79 @@
+{
+  description = "A Nix-flake-based Python development environment";
+
+  inputs.nixpkgs.url = "https://flakehub.com/f/NixOS/nixpkgs/0.1";
+
+  outputs = inputs:
+    let
+      supportedSystems = [ "x86_64-linux" "aarch64-linux" "x86_64-darwin" "aarch64-darwin" ];
+      forEachSupportedSystem = f: inputs.nixpkgs.lib.genAttrs supportedSystems (system: f {
+        pkgs = import inputs.nixpkgs { inherit system; };
+      });
+
+      /*
+       * Change this value ({major}.{min}) to
+       * update the Python virtual-environment
+       * version. When you do this, make sure
+       * to delete the `.venv` directory to
+       * have the hook rebuild it for the new
+       * version, since it won't overwrite an
+       * existing one. After this, reload the
+       * development shell to rebuild it.
+       * You'll see a warning asking you to
+       * do this when version mismatches are
+       * present. For safety, removal should
+       * be a manual step, even if trivial.
+       */
+      version = "3.13";
+    in
+    {
+      devShells = forEachSupportedSystem ({ pkgs }:
+        let
+          concatMajorMinor = v:
+            pkgs.lib.pipe v [
+              pkgs.lib.versions.splitVersion
+              (pkgs.lib.sublist 0 2)
+              pkgs.lib.concatStrings
+            ];
+
+          python = pkgs."python${concatMajorMinor version}";
+        in
+        {
+          default = pkgs.mkShell {
+            venvDir = ".venv";
+
+            postShellHook = ''
+              venvVersionWarn() {
+              	local venvVersion
+              	venvVersion="$("$venvDir/bin/python" -c 'import platform; print(platform.python_version())')"
+
+              	[[ "$venvVersion" == "${python.version}" ]] && return
+
+              	cat <<EOF
+              Warning: Python version mismatch: [$venvVersion (venv)] != [${python.version}]
+                       Delete '$venvDir' and reload to rebuild for version ${python.version}
+              EOF
+              }
+
+              venvVersionWarn
+            '';
+
+            packages = with python.pkgs; [
+              venvShellHook
+              pip
+
+              /* Add whatever else you'd like here. */
+              # pkgs.basedpyright
+
+              # pkgs.black
+              /* or */
+              # python.pkgs.black
+
+              # pkgs.ruff
+              /* or */
+              # python.pkgs.ruff
+            ];
+          };
+        });
+    };
+}