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:

$ sudo apt-get install python3 python3-pip watchman

We tested Pyre on Ubuntu 16.04 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.