pyright

pyright is a static type checker for Python created by Microsoft that provides fast, precise type analysis, error detection, and advanced language features for large codebases. It focuses on performance, configurability, and IDE integration, powering features like autocompletion and code navigation in Visual Studio Code through the Pylance extension.

Core Functionality

Type Checking Engine

• Performance-Optimized: Written in TypeScript/Node.js for speed
• Watch Mode: Provides real-time type checking during development
• Incremental Analysis: Only rechecks modified files and dependencies
• Parallel Processing: Utilizes multiple CPU cores for faster analysis
• Memory Efficiency: Designed for large codebases with minimal overhead

Analysis Capabilities

• Type Inference: Deduces types without explicit annotations
• Flow Analysis: Tracks variable types through control flow paths
• Source Mapping: Precisely maps errors to specific locations
• Import Resolution: Correctly handles package imports and namespace packages
• Type Stub Integration: Works with typeshed and custom stub files

Pros

• Superior Performance: Significantly faster than other Python type checkers
• First-Class IDE Integration: Tightly integrated with VS Code via Pylance
• Regular Updates: Frequent releases with new features and improvements
• Corporate Backing: Maintained by Microsoft with dedicated resources
• Granular Configuration: Highly customizable for different project needs

Cons

• Less Community Adoption: Fewer online resources compared to mypy
• Extension Focused: Primary design for IDE integration rather than CLI use
• TypeScript Implementation: Requires Node.js runtime

Usage Examples

# Install pyright
uv pip install pyright

# Basic type checking
pyright src/

# Specify configuration
pyright --project ./pyrightconfig.json

# Watch mode for continuous checking
pyright --watch

Learn More

• Official Documentation
• Pylance Extension for VS Code
• pyright GitHub Repository