Greynir runs on CPython 3.6 or newer, and on PyPy 3.6 or newer (more info on PyPy here).

On GNU/Linux and similar systems, you may need to have python3-dev installed on your system:

# Debian or Ubuntu:
$ sudo apt-get install python3-dev

Depending on your system, you may also need to install libffi-dev:

# Debian or Ubuntu:
$ sudo apt-get install libffi-dev

On Windows, you may need the latest Visual Studio Build Tools, specifically the Visual C++ build tools, installed on your PC along with the Windows 10 SDK.

Install with pip

To install Greynir:

$ pip install reynir

…or if you have both Python2 and Python3 available on your system:

$ pip3 install reynir

…or if you want to be able to edit Greynir’s source code in-place, install git and git-lfs (as described here) and do the following:

$ mkdir ~/github
$ cd ~/github
$ git clone
$ cd GreynirPackage
$ git lfs install
$ git pull
$ pip install -e .

On the most common Linux x86_64/amd64 systems, pip will download and install a binary wheel. On other systems, a source distribution will be downloaded and compiled to binary.

Pull requests are welcome in the project’s GitHub repository.

Install into a virtualenv

In many cases, you will want to maintain a separate Python environment for your project that uses Greynir. For this, you can use virtualenv (if you haven’t already, install it with pip install virtualenv):

$ virtualenv -p python3 venv

# Enter the virtual environment
$ source venv/bin/activate

# Install Greynir into it
$ pip install reynir

$ python
    [ Use Python with Greynir ]

# Leave the virtual environment
$ deactivate

On Windows:

C:\MyProject> virtualenv venv

REM Enter the virtual environment
C:\MyProject> venv/Scripts/activate

REM Install Greynir into it
(venv) C:\MyProject> pip install reynir

(venv) C:\MyProject> python
    REM [ Use Python with Greynir ]

REM Leave the virtual environment
(venv) C:\MyProject> deactivate

More information about virtualenv is available here.