python-matheval is the second example project for my book in progress on Continuous Delivery.
It is a python-based web service that evaluates a tree of mathematical expresions. For example it turns the JSON tree
["*", ["+", 2, 3], 4]
which corresponds to (2 + 3) * 4, into the result, 20.
It is a flask application, packaged with dh-virtualenv, run by gunicorn and controlled through systemd.