Book Image

Django 4 By Example - Fourth Edition

By : Antonio Melé
4.6 (5)
Book Image

Django 4 By Example - Fourth Edition

4.6 (5)
By: Antonio Melé

Overview of this book

Django 4 By Example is the 4th edition of the best-selling franchise that helps you build web apps. This book will walk you through the creation of real-world applications, solving common problems, and implementing best practices using a step-by-step approach. You'll cover a wide range of web app development topics as you build four different apps: A blog application: Create data models, views, and URLs and implement an admin site for your blog. Create sitemaps and RSS feeds and implement a full-text search engine with PostgreSQL. A social website: Implement authentication with Facebook, Twitter, and Google. Create user profiles, image thumbnails, a bookmarklet, and an activity stream. Implement a user follower system and add infinite scroll pagination to your website. An e-commerce application: Build a product catalog, a shopping cart, and asynchronous tasks with Celery and RabbitMQ. Process payments with Stripe and manage payment notifications via webhooks. Build a product recommendation engine with Redis. Create PDF invoices and export orders to CSV. An e-learning platform: Create a content management system to manage polymorphic content. Cache content with Memcached and Redis. Build and consume a RESTful API. Implement a real-time chat using WebSockets with ASGI. Create a production environment using NGINX, uWSGI and Daphne with Docker Compose. This is a practical book that will have you creating web apps quickly.
Table of Contents (20 chapters)
18
Other Books You May Enjoy
19
Index

Using signals for denormalizing counts

There are some cases when you may want to denormalize your data. Denormalization is making data redundant in such a way that it optimizes read performance. For example, you might be copying related data to an object to avoid expensive read queries to the database when retrieving the related data. You have to be careful about denormalization and only start using it when you really need it. The biggest issue you will find with denormalization is that it’s difficult to keep your denormalized data updated.

Let’s take a look at an example of how to improve your queries by denormalizing counts. You will denormalize data from your Image model and use Django signals to keep the data updated.

Working with signals

Django comes with a signal dispatcher that allows receiver functions to get notified when certain actions occur. Signals are very useful when you need your code to do something every time something else happens. Signals...