Guide for using ty, the extremely fast Python type checker and language
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 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 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 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: # 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: [[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 mypy . → ty check mypy --strict . → ty check --error-on-warning mypy path/to/file.py → ty check path/to/file.py Pyright → ty 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: # 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/
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