auto-typing-final

Auto-fixer for Python code that adds typing.Final annotation to variable assignments inside functions that are not reassigned, and removes the annotation from variables that are mutated.

 def foo() -> None:
-    a = 2
+    a: typing.Final = 2

-    b: typing.Final = 2
+    b = 2
     b = 3

Basically, this, but handles different operations (like usage of nonlocal, augmented assignments: +=, etc) as well.

• Keeps mypy happy.
• Ignores global variables to avoid confusion with the type aliases like Fruit = Apple | Banana.
• Ignores class variables: it is common to use typing.ClassVar instead of typing.Final.
• Adds global import if it's not imported yet.
• Inspects one file at a time.

How To Use

Having uv installed:

uvx auto-typing-final .

or:

pipx run auto-typing-final .

Options

You can specify --check flag to check the files instead of actually fixing them:

auto-typing-final . --check

Also, you can choose import style from two options: typing-final (default) and final:

auto-typing-final . --import-style typing-final

• typing-final enforces import typing and typing.Final,
• final enforces from typing import Final and Final.

VS Code Extension

The extension uses LSP server bundled with the CLI. To get started, add auto-typing-final to your project:

uv add auto-typing-final --dev

or:

poetry add auto-typing-final --group=dev

After that, install the extension: https://marketplace.visualstudio.com/items?itemName=vrslev.auto-typing-final. In Python environments that have auto-typing-final installed, extension will be activated automatically.

Import style can be configured in settings: "auto-typing-final.import-style": "typing-final" or "auto-typing-final.import-style": "final".

Library code of currently activated environment will be ignored (for example, .venv/bin/python is active interpreter, all code inside .venv will be ignored).