# ty

[![ty](https://img.shields.io/endpoint?url=https://raw.githubusercontent.com/astral-sh/ty/main/assets/badge/v0.json)](https://github.com/astral-sh/ty)
[![PyPI](https://img.shields.io/pypi/v/ty.svg)](https://pypi.python.org/pypi/ty)
[![Discord](https://img.shields.io/badge/Discord-%235865F2.svg?logo=discord&logoColor=white)](https://discord.com/invite/astral-sh)

An extremely fast Python type checker and language server, written in Rust.

<br />

<p align="center">
  <img alt="Shows a bar chart with benchmark results." width="500px" src="https://raw.githubusercontent.com/astral-sh/ty/main/docs/assets/ty-benchmark-cli-light.svg">
</p>

<p align="center">
  <i>Type checking the <a href="https://github.com/home-assistant/core">home-assistant</a> project without caching.</i>
</p>

<br />

ty is backed by [Astral](https://astral.sh), the creators of
[uv](https://github.com/astral-sh/uv) and [Ruff](https://github.com/astral-sh/ruff).

ty is currently in [beta](https://github.com/astral-sh/ty/blob/0.0.59/README.md#version-policy).

## Highlights

- 10x - 100x faster than mypy and Pyright
- Comprehensive [diagnostics](https://docs.astral.sh/ty/features/diagnostics/) with rich contextual information
- Configurable [rule levels](https://docs.astral.sh/ty/rules/), [per-file overrides](https://docs.astral.sh/ty/reference/configuration/#overrides), [suppression comments](https://docs.astral.sh/ty/suppression/), and first-class project support
- Designed for adoption, with support for [redeclarations](https://docs.astral.sh/ty/features/type-system/#redeclarations) and [partially typed code](https://docs.astral.sh/ty/features/type-system/#gradual-guarantee)
- [Language server](https://docs.astral.sh/ty/features/language-server/) with code navigation, completions, code actions, auto-import, inlay hints, on-hover help, etc.
- Fine-grained [incremental analysis](https://docs.astral.sh/ty/features/language-server/#fine-grained-incrementality) designed for fast updates when editing files in an IDE
- Editor integrations for [VS Code](https://docs.astral.sh/ty/editors/#vs-code), [PyCharm](https://docs.astral.sh/ty/editors/#pycharm), [Neovim](https://docs.astral.sh/ty/editors/#neovim) and more
- Advanced typing features like first-class [intersection types](https://docs.astral.sh/ty/features/type-system/#intersection-types), advanced [type narrowing](https://docs.astral.sh/ty/features/type-system/#top-and-bottom-materializations), and
    [sophisticated reachability analysis](https://docs.astral.sh/ty/features/type-system/#reachability-based-on-types)

## Getting started

Run ty with [uvx](https://docs.astral.sh/uv/guides/tools/#running-tools) to get started quickly:

```shell
uvx ty check
```

Or, check out the [ty playground](https://play.ty.dev) to try it out in your browser.

To learn more about using ty, see the [documentation](https://docs.astral.sh/ty/).

## Installation

To install ty, see the [installation](https://docs.astral.sh/ty/installation/) documentation.

To add the ty language server to your editor, see the [editor integration](https://docs.astral.sh/ty/editors/) guide.

## Getting help

If you have questions or want to report a bug, please open an
[issue](https://github.com/astral-sh/ty/issues) in this repository.

You may also join our [Discord server](https://discord.com/invite/astral-sh).

## Contributing

Development of this project takes place in the [Ruff](https://github.com/astral-sh/ruff) repository
at this time. Please [open pull requests](https://github.com/astral-sh/ruff/pulls) there for changes
to anything in the `ruff` submodule (which includes all of the Rust source code).

See the
[contributing guide](https://github.com/astral-sh/ty/blob/0.0.59/CONTRIBUTING.md) for more details.

## Version policy

ty uses `0.0.x` versioning. ty does not yet have a stable API; breaking changes, including changes
to diagnostics, may occur between any two versions. See the [type system support](https://github.com/astral-sh/ty/issues/1889)
tracking issue for a detailed overview of currently supported features.

## FAQ

<!-- We intentionally use smaller headings for the FAQ items -->

<!-- markdownlint-disable MD001 -->

#### Which Python versions does ty support?

ty officially supports type checking code that targets Python 3.10 and later. Earlier versions
(Python 3.7 through 3.9) can still be selected, but may result in false negatives or false
positives due to a lack of bundled standard library stubs.

The target version is independent of the Python version used to install ty. For example, ty
installed from PyPI using Python 3.8 or later can type check code targeting Python 3.7; the
standalone installer does not require Python at all.

#### Why is ty doing \_\_\_\_\_?

See our [typing FAQ](https://docs.astral.sh/ty/reference/typing-faq).

#### How do you pronounce ty?

It's pronounced as "tee - why" ([`/tiː waɪ/`](https://en.wikipedia.org/wiki/Help:IPA/English#Key))

#### How should I stylize ty?

Just "ty", please.

<!-- markdownlint-enable MD001 -->

## License

ty is licensed under the MIT license ([LICENSE](https://github.com/astral-sh/ty/blob/0.0.59/LICENSE) or
<https://opensource.org/licenses/MIT>).

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in ty
by you, as defined in the MIT license, shall be licensed as above, without any additional terms or
conditions.

<div align="center">
  <a target="_blank" href="https://astral.sh" style="background:none">
    <img src="https://raw.githubusercontent.com/astral-sh/uv/main/assets/svg/Astral.svg" alt="Made by Astral">
  </a>
</div>
