Preface

Welcome to Learning Flask, the book that will teach you the necessary skills to build web applications with Flask, a lightweight Python web framework. This book takes an example-driven approach that is designed to get you started quickly. The practical examples are balanced with just the right amount of background information to ensure that you understand not only the how, but also the why of Flask development.

Flask was originally released by Armin Ronacher as part of an elaborate April Fool's Day prank in 2010. The project touted itself as, "The next generation python micro web-framework," and lampooned features made popular by similar microframeworks. Although Flask was intended as a prank, the authors were caught by surprise when many people expressed serious interest in the project.

Flask is a microframework that is built on top of two excellent libraries: the Jinja2 templating engine, and the Werkzeug WSGI toolkit. Despite being a relative new-comer compared to other frameworks, such as Django, and Pylons, Flask has garnered a large and loyal following. Flask provides powerful tools for common web development tasks and encourages a bring-your-own-library approach for everything else, allowing programmers the flexibility to pick and choose the best components for their application. Every Flask app is different, and as the project's documentation states, "Flask is Fun".

The Flask microframework represents a departure in terms of design and API from most other popular Python web frameworks, which has led many developers that are new to Flask to ask, "What is the right way to build an app?" Flask does not offer any strong opinions on how we, the developers, should build our app. Instead, it provides opinions on what you need to build an app. Flask can be thought of as a collection of objects and functions to deal with common web tasks, such as routing URLs to code, processing request data, and rendering templates. While the level of flexibility that Flask provides is liberating, it can also lead to confusion and poor designs.

The purpose of this book is to help you see this flexibility as opportunity. Over the course of this book, we will be building and progressively enhancing a Flask-powered blogging site. New concepts will be introduced through the addition of new features to the site. By the end of the book, we will have created a fully-featured website, and you will have a strong working knowledge of Flask and the ecosystem of its commonly-used extensions and libraries.