Python Type Checking with ty

ty is an extremely fast Python type checker from Astral (makers of Ruff).

Quick Start

# Run type checker (no install needed)
uvx ty check

# Check specific files
uvx ty check src/ tests/

Installation (Optional)

# Install globally
uv tool install ty@latest

# Update
uv tool upgrade ty

Common Tasks

# Watch mode - auto-recheck on file changes
ty check --watch

# Target specific Python version
ty check --python-version 3.11

# Concise output
ty check --format concise

# Exclude test files
ty check --exclude "**/test_*.py"

Configuration File

Create ty.toml in project root (auto-discovered):

python-version = "3.11"
exclude = ["**/test_*.py", "**/__pycache__/**"]
format = "concise"

CI/CD

# Strict CI check
ty check --error all --error-on-warning --no-progress

Exit codes: 0 = success, 1 = errors found, 2 = internal error

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Advanced Options

Severity Control

ty check --error all        # All issues as errors
ty check --warn typing      # Typing issues as warnings
ty check --ignore unused    # Ignore unused imports

Environment Targeting

ty check --python /path/to/python    # Specific interpreter
ty check --venv /path/to/venv        # Target virtualenv
ty check --python-platform linux     # Cross-platform check
ty check --extra-search-path ./stubs/

Output Formats

ty check --format full       # Detailed (default)
ty check --format concise    # Compact
ty check --format github     # GitHub Actions annotations
ty check --format gitlab     # GitLab CI format
ty check --color never       # No colors
ty check --no-progress       # Hide progress bar
ty check -v                  # Verbose
ty check -q                  # Quiet

Other Commands

ty server                              # Start LSP server
ty version                             # Show version
ty generate-shell-completion zsh       # Shell completions