Developing for FlexMeasures

This page instructs developers who work on FlexMeasures how to set up the development environment. Furthermore, we discuss several guidelines and best practices.

Getting started

Virtual environment

Using a virtual environment is best practice for Python developers. We also strongly recommend using a dedicated one for your work on FlexMeasures, as our make target (see below) will use pip-sync to install dependencies, which could interfere with some libraries you already have installed.

  • Make a virtual environment: python3.8 -m venv flexmeasures-venv or use a different tool like mkvirtualenv or virtualenvwrapper. You can also use an Anaconda distribution as base with conda create -n flexmeasures-venv python=3.8.

  • Activate it, e.g.: source flexmeasures-venv/bin/activate


Install all dependencies including the ones needed for development:

make install-for-dev


Follow the configuration Quickstart advice in Getting started and Configuration.

Loading data

If you have a SQL Dump file, you can load that:

psql -U {user_name} -h {host_name} -d {database_name} -f {file_path}

Run locally

Now, to start the web application, you can run:

flexmeasures run



And access the server at http://localhost:5000


You can run automated tests with:

make test

which behind the curtains installs dependencies and calls pytest.

A coverage report can be created like this:

pytest --cov=flexmeasures --cov-config .coveragerc

You can add –cov-report=html after which a htmlcov/index.html is generated.

It’s also possible to use:

python test


We use setuptool_scm for versioning, which bases the FlexMeasures version on the latest git tag and the commits since then.

So as a developer, it’s crucial to use git tags for versions only.

We use semantic versioning, and we always include the patch version, not only max and min, so that setuptools_scm makes the correct guess about the next minor version. Thus, we should use 2.0.0 instead of 2.0.

See for more commentary on the development versions.

Our API has its own version, which moves much slower. This is important to explicitly support outside apps who were coded against older versions.

Auto-applying formatting and code style suggestions

We use Black to format our Python code and Flake8 to enforce the PEP8 style guide and linting. We also run mypy on many files to do some static type checking.

We do this so real problems are found faster and the discussion about formatting is limited. All of these can be installed by using pip, but we recommend using them as a pre-commit hook. To activate that behaviour, do:

pip install pre-commit
pre-commit install

in your virtual environment.

Now each git commit will first run flake8, then black and finally mypy over the files affected by the commit (pre-commit will install these tools into its own structure on the first run).

This is also what happens automatically server-side when code is committed to a branch (via Github Actions), but having those tests locally as well will help you spot these issues faster.

If flake8, black or mypy propose changes to any file, the commit is aborted (saying that it “failed”). The changes proposed by black are implemented automatically (you can review them with git diff). Some of them might even resolve the flake8 warnings :)

A hint about using notebooks

If you edit notebooks, make sure results do not end up in git:

conda install -c conda-forge nbstripout
nbstripout --install

(on Windows, maybe you need to look closer at

A hint for Unix developers

I added this to my ~/.bashrc, so I only need to type fm to get started and have the ssh agent set up, as well as up-to-date code and dependencies in place.

    eval `ssh-agent -s`
    ssh-add ~/.ssh/id_bitbucket
    cd ~/workspace/flexmeasures
    git pull  # do not use if any production-like app runs from the git code
    workon flexmeasures-venv  # this depends on how you created your virtual environment
    make install-for-dev


All paths depend on your local environment, of course.