Pyright

Pyright is an open‑source static type checker for Python, developed by Microsoft and implemented in TypeScript. It provides fast, scalable type analysis for Python projects and is used as the underlying type‑checking engine for Pylance, the Visual Studio Code Python extension, as well as a standalone command‑line tool and a language server.

Features of Pyright include static type checking with Python’s typing system (PEP 484, 585, and related features). It supports type hints, type inference, generics, Protocols, TypedDict, and overloads, along with support for stub files (.pyi). Pyright performs import resolution and type checking across modules, with incremental analysis and caching to handle large codebases. It offers a strict mode and configurable levels of checking, and projects can be configured with a pyrightconfig.json file to set the Python version, search paths, excludes, and other options.

Usage and integration: Pyright is available as a command-line tool (pyright) and as a language server (pyright-langserver) for editor integrations. It can be run on a project to emit diagnostics and can be integrated into continuous integration workflows. It recognizes a per‑project pyrightconfig.json and supports settings for Python version, type checking mode, and module discovery.

Background and licensing: Pyright is maintained by Microsoft and released under the MIT license. The source code is hosted on GitHub, and the package is distributed via npm. It is widely used in Python development workflows, particularly in conjunction with the Pylance extension in Visual Studio Code. It serves as a fast, user‑friendly tool for enforcing type correctness in Python projects.