Book Image

Web Development with Django - Second Edition

By : Ben Shaw, Saurabh Badhwar, Chris Guest, Bharath Chandra K S
4.7 (3)
Book Image

Web Development with Django - Second Edition

4.7 (3)
By: Ben Shaw, Saurabh Badhwar, Chris Guest, Bharath Chandra K S

Overview of this book

Do you want to develop reliable and secure applications that stand out from the crowd without spending hours on boilerplate code? You’ve made the right choice trusting the Django framework, and this book will tell you why. Often referred to as a “batteries included” web development framework, Django comes with all the core features needed to build a standalone application. Web Development with Django will take you through all the essential concepts and help you explore its power to build real-world applications using Python. Throughout the book, you’ll get the grips with the major features of Django by building a website called Bookr – a repository for book reviews. This end-to-end case study is split into a series of bitesize projects presented as exercises and activities, allowing you to challenge yourself in an enjoyable and attainable way. As you advance, you'll acquire various practical skills, including how to serve static files to add CSS, JavaScript, and images to your application, how to implement forms to accept user input, and how to manage sessions to ensure a reliable user experience. You’ll cover everyday tasks that are part of the development cycle of a real-world web application. By the end of this Django book, you'll have the skills and confidence to creatively develop and deploy your own projects.
Table of Contents (19 chapters)

Custom field validation and cleaning

We have seen how a Django form converts values from an HTTP request, which are strings, into Python objects. In a non-custom Django form, the target type is dependent on the field class. For example, the Python type derived from IntegerField is int, and string values are given to us verbatim, as the user entered them. But, we can also implement methods on our Form class to alter the output values from our fields in any way we choose. This allows us to clean or filter the user’s input data to fit what we expect better. We could round an integer to the nearest multiple of 10 so that it fits into a batch size for ordering specific items. Or, we could transform an email address into lowercase so that the data is consistent for searching.

We can also implement some custom validators. We’ll look at a couple of different ways of validating fields: by writing a custom validator, and by writing a custom clean method for the field. Each method...