Getting Started

Welcome to the wonderful world of static typing! This guide will get you from zero to a simple project that is type checked with Pyre.

Requirements

To get started, you need Python 3.6 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.

Setting up a Project

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.

Running Pyre

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.