Static type checker for Python

Speed

Pyright is a fast type checker meant for large Python source bases. It can run in a “watch” mode and performs fast incremental updates when files are modified.

No Dependency on Python Environment

Pyright does not require a Python environment or imported third-party packages to be installed.

Configurability

Pyright supports configuration files that provide granular control over settings. Different “execution environments” can be associated subdirectories within a source base. Each environment can specify different module search paths, python language versions, and platform targets.

Type Checking Features

Pyright supports:

• PEP 484 type hints including generics
• PEP 526 syntax for variable annotations
• PEP 544 structural subtyping
• Type inference for function return values, instance variables, class variables, and globals
• Smart type constraints that understand conditional code flow constructs like if/else statements

Built-in Type Stubs

Pyright includes a recent copy of the stdlib type stubs from Typeshed. It can be configured to use another (perhaps more recent or modified) copy of the Typeshed type stubs. Of course, it also works with custom type stub files that are part of your project.

Command-line Tool or VS Code Extension

Pyright includes both a command-line tool and a Language Server Protocol plugin for VS Code.

Documentation

• Getting Started
• Command-line Options
• Configuration
• Import Resolution
• Building & Debugging
• Pyright Internals

Limitations

Pyright currently provides support for Python 3.0 and newer. There is currently no plan to support older versions.

Pyright is a work in progress. Type-checking capabilities are not fully implemented. For a list of incomplete functionality, refer to the TODO list below.

FAQ

Q: What is the difference between pyright and the Microsoft Python VS Code plugin?

A: The Python VS Code plugin is the official Python support extension for VS Code. It is officially supported by a team of engineers at Microsoft. It supports a diverse array of features including debugging, linter plugins, type checking plugins, and much more. Pyright is focused entirely on type checking. It is a side project with no dedicated team.

Q: What is the difference between pyright and the Microsoft Python Language Server?

A: The Microsoft Python Language Server is a language server protocol (LSP) implementation that works with the Microsoft Python VS Code plugin, and it is officially supported by a team of Microsoft engineers. It also provides type checking capabilities. Pyright provides overlapping functionality but includes some unique features such as more configurabilty, command-line execution, and better performance.

Installation

You can install the latest-published version of the Pyright VS Code extension directly from VS Code. Simply open the extensions panel and search for pyright.

The latest version of the command-line tool can be installed with npm: npm i pyright

To install it globally: npm i -g pyright

To run the command-line tool: npx pyright <options>

TODO

Pyright is a work in progress. The following functionality is not yet finished. If you would like to contribute to any of these areas, contact the maintainers of the repo.

• Validate that all abstract methods are overridden
• Type analysis support for generators
• Type analysis support for coroutines
• Type analysis support for async functions and lambdas
• Support for old-style type annotations within comments
• Address the many TODO comments in the code
• Provide switch that treats instance variables and methods that begin with underscore as private
• Validate parameters for magic functions
• Synthesize TypeVar param and return types for lambdas where possible
• Validate that overridden methods in subclass have same signature as base class methods
• Verify that exception classes inherit from base Exception
• Add support for inference of subclass type vars based on method parameter types declared in subclass
• Validate consistency of subclass type vars across all declared methods
• Add support for type hints on var-arg parameters
• Add support for NoReturn type
• Flag assignments to read-only values (None, True, False, __debug__) as errors
• Revamp support for properties - model with Descriptor protocol, detect missing setter
• Add numeric codes to diagnostics and a configuration mechanism for disabling errors by code

Contributing

This project welcomes contributions and suggestions. Most contributions require you to agree to a Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us the rights to use your contribution. For details, visit https://cla.microsoft.com.

When you submit a pull request, a CLA-bot will automatically determine whether you need to provide a CLA and decorate the PR appropriately (e.g., label, comment). Simply follow the instructions provided by the bot. You will only need to do this once across all repos using our CLA.

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact opencode@microsoft.com with any additional questions or comments.