Pyre is a performant type checker for Python compliant with PEP 484. Pyre can analyze codebases with millions of lines of code incrementally – providing instantaneous feedback to developers as they write code. You can try it out on examples in the Pyre Playground.

Pyre ships with Pysa, a security focused static analysis tool we've built on top of Pyre that reasons about data flows in Python applications. Please refer to our documentation to get started with our security analysis.

Pysa is also available on the GitHub Marketplace as a Github Action

To get started, you need Python 3.8 or later and watchman working on your system. On MacOS you can get everything with homebrew:

$ brew install python3 watchman

On Ubuntu, Mint, or Debian; use apt-get and homebrew:

$ sudo apt-get install python3 python3-pip python3-venv
$ brew install watchman

We tested Pyre on Ubuntu 18.04.5 LTS, CentOS 7, as well as OSX 10.11 and later.

We start by creating an empty project directory and setting up a virtual environment:

$ mkdir my_project && cd my_project
$ python3 -m venv ~/.venvs/venv
$ source ~/.venvs/venv/bin/activate
(venv) $ pip install pyre-check

Next, we teach Pyre about our new project:

(venv) $ pyre init

This command will set up a configuration for Pyre (.pyre_configuration) as well as watchman (.watchmanconfig) in your project's directory. Accept the defaults for now – you can change them later if necessary.

We are now ready to run Pyre:

(venv) $ echo "i: int = 'string'" > test.py
(venv) $ pyre
 ƛ Found 1 type error!
test.py:1:0 Incompatible variable type [9]: i is declared to have type `int` but is used as type `str`.

This first invocation will start a daemon listening for filesystem changes – type checking your project incrementally as you make edits to the code. You will notice that subsequent invocations of pyre will be faster than the first one.

For more detailed documentation, see https://pyre-check.org.

See CONTRIBUTING.md for how to help out.

Pyre is licensed under the MIT license.