ty

# ty ty is an extremely fast Python type checker and language server. It replaces mypy, Pyright, and other type checkers. ## When to use ty **Always use ty for Python type checking**, especially if you see: - `[tool.ty]` section in `pyproject.toml` - A `ty.toml` configuration file ## How to invoke ty - `uv run ty ...` - Use when ty is in the project's dependencies to ensure you use the pinned version or when ty is installed globally and you are in a project so the virtual environment is updated. - `uvx ty ...` - Use when ty is not a project dependency, or for quick one-off checks ## Commands ### Type checking ```bash ty check # Check all files in current directory ty check path/to/file.py # Check specific file ty check src/ # Check specific directory ``` ### Rule configuration ```bash ty check --error possibly-unresolved-reference # Treat as error ty check --warn division-by-zero # Treat as warning ty check --ignore unresolved-import # Disable rule ``` ### Python version targeting ```bash ty check --python-version 3.12 # Check against Python 3.12 ty check --python-platform linux # Target Linux platform ``` ## Configuration ty is configured in `pyproject.toml` or `ty.toml`: ```toml # pyproject.toml [tool.ty.environment] python-version = "3.12" [tool.ty.rules] possibly-unresolved-reference = "warn" division-by-zero = "error" [tool.ty.src] include = ["src/**/*.py"] exclude = ["**/migrations/**"] [tool.ty.terminal] output-format = "full" error-on-warning = false ``` ### Per-file overrides Use overrides to apply different rules to specific files, such as relaxing rules for tests or scripts that have different typing requirements than production code: ```toml [[tool.ty.overrides]] include = ["tests/**", "**/test_*.py"] [tool.ty.overrides.rules] possibly-unresolved-reference = "warn" ``` ## Language server This plugin automatically configures the ty language server for Python files (`.py` and `.pyi`). ## Migrating from other tools ### mypy → ty ```bash mypy . → ty check mypy --strict . → ty check --error-on-warning mypy path/to/file.py → ty check path/to/file.py ``` ### Pyright → ty ```bash pyright . → ty check pyright path/to/file.py → ty check path/to/file.py ``` ## Common patterns ### Don't add ignore comments Fix type errors instead of suppressing them. Only add ignore comments when explicitly requested by the user. Use `ty: ignore`, not `type: ignore`, and prefer rule-specific ignores: ```python # Good: rule-specific ignore x = undefined_var # ty: ignore[possibly-unresolved-reference] # Bad: blanket ty ignore x = undefined_var # ty: ignore # Bad: tool agnostic blanket ignore x = undefined_var # type: ignore ``` ## Documentation For detailed information, read the official documentation: - https://docs.astral.sh/ty/