Mastering Flask Web Development - Second Edition

Blueprints

In Flask, a blueprint is a method of extending an existing Flask app. They provide a way of combining groups of views with common functionality and allow developers to break their app down into different components. In our architecture, the blueprints will act as our controllers.

Views are registered to a blueprint; a separate template and static folder can be defined for it, and when it has all the desired content in it, it can be registered on the main Flask app to add the blueprint's content. A blueprint acts much like a Flask app object, but is not actually a self-contained app. This is how Flask extensions provide view functions. To get an idea of what blueprints are, here is a very simple example:

from flask import Blueprint ...