About this skill
---
name: mcore-linting-and-formatting
description: Linting and formatting for Megatron-LM. Covers running autoformat.sh, tools (ruff, black, isort, pylint, mypy), and code style rules.
license: Apache-2.0
when_to_use: Running linting or autoformat; fixing style violations before a PR; 'pre-commit fails', 'ruff error', 'isort', 'mypy', 'style violation', 'how do I format', 'autoformat.sh'.
metadata:
author: Philip Petrakian <[email protected]>
---
# Linting and Formatting
---
## Running the Formatter
Run before opening a PR:
```bash
# Check mode (no changes applied)
BASE_REF=main CHECK_ONLY=true SKIP_DOCS=false bash tools/autoformat.sh
# Fix mode
BASE_REF=main CHECK_ONLY=false bash tools/autoformat.sh
```
Tools invoked: `black`, `isort`, `pylint`, `ruff`, `mypy`.
---
## Import Ordering
After editing imports in any Python files, always run `uv run isort` on those
files before committing:
```bash
uv run isort <file1>.py <file2>.py
```
---
## Setting Up the Linting Group
Inside the container:
```bash
uv sync --locked --only-group linting
```
This installs `ruff`, `black`, `isort`, `pylint` — the same tools used by
`tools/autoformat.sh` and CI's `linting` job.
---
## Code Style Rules
- **Type hints**: required on all public API functions. Use `X | None`, not `Optional[X]`.
- **Docstrings**: Google-style on all public classes and functions.
- **Naming**: follow Python conventions — `snake_case` for functions and variables, `PascalCase` for classes.
- **Line length**: 119 characters (configured in `pyproject.toml`).
- **No bare `except`**: always catch specific exception types.