Development Environment


To get an overview on how to set up a development environment, please read Development Quick Start or see NixOS Virtualbox Dev VM to learn how to set up a NixOS development VM from start to finish.

To get a consistent development environment, we use Nix to install Python and the project dependencies. The development environment also includes PostgreSQL, linters, a SASS compiler and pytest for running the tests.

The following code snippets are written for ekklesia-portal but also work for ekklesia-voting when you change the project name.

Install Nix

Installation instructions taken from Getting Nix. See the link for other installation methods.

Nix is currently supported on Linux and Mac. The quickest way to install Nix is to open a terminal and run the following command (as a user other than root with sudo permission):

curl -L | sh

Make sure to follow the instructions output by the script. The installation script requires that you have sudo access to root.

Install Lorri

A good way to get a development shell is to use Lorri which improves the builtin nix-shell command. Another option is to use nix-direnv as described in the next section.

Install lorri (also works for updates):

nix-env -i lorri

This is enough to use lorri shell needed for the quick start section below.

We also recommend using the direnv integration. This will automatically enter the development shell when changing to the project directory. Please follow the Lorri Installation Instructions.

Setting up nix-direnv

Instead of lorri (described above), you can also use direnv <>`_ with nix-direnv to get a automatically updating development shell. See the linked pages for instruction on how to set them up.

Setting up the Cachix Binary Cache

To speed up installation, you should add the edemocracy binary cache hosted on Cachix.

If your user can edit Nix config files (when using a single-user installation on a non-NixOS system, for example), just install the Cachix client and add the edemocracy cache:

nix-env -i cachix
cachix use edemocracy

If cachix cannot change the config, it will instructions on how to do it. On NixOS, you have to run cachix as root (sudo cachix use edemocracy) or another trusted Nix user.

Running PostgreSQL as User

You can run a PostgreSQL database server with your user permissions if you don’t want to use an existing database server. Run the pg_ctl commands from the nix shell.

Run as user:

pg_ctl -D ~/postgresql init
postgres -D ~/postgresql -k /tmp -h ''

Create database (in another terminal):

createdb -h /tmp ekklesia_portal

You can connect to the database with psql now:

psql -h /tmp ekklesia_portal

Use the following connection string in the app config file:

  uri: "postgresql+psycopg2:///ekklesia_portal?host=/tmp"

Updating The Development Environment

lorri shell always installs changed dependencies and tools before entering the development shell which takes some seconds.

When using the direnv integration, running lorri daemon in the background automatically updates the development shell when something changes. Press Enter in the development shell to trigger the first daemon build or to see the changes in the shell made by direnv.

You can also trigger an update by running lorri watch --once if you don’t want to run lorri daemon.

Editor / IDE Integration

Tested with VSCode, Pycharm

Run this to build the environment:


This creates a directory pyenv that is similar to a Python virtualenv. The Environment should be picked up by the IDE using the Python interpreter in the directory. A restart may be required.