Flask is a wonderful framework for people who want to write a very quick single-file application in order to prototype an API or to build a drop-dead simple website. What isn't immediately obvious, however, is just how flexible and adept Flask is at growing in larger, more modular application structures that are a necessity once the single-module layout becomes more burdensome than convenient. The major points that we will cover in this chapter are as follows:
How to convert a module-based Flask application to a package-based layout
How to implement Flask blueprints on top of a package-based application structure
How to ensure that our resulting application can be run with the built-in Werkzeug development server