The third edition of this trusted guide demonstrates the practical advantages of test-driven development (TDD) with Python and describes how to develop a real web application. You'll learn how to write and run tests before building each part of your app and then develop the minimum amount of code required to pass those tests. In the process, author Harry Percival teaches software and web developers the basics of Django, Selenium, Git, JavaScript, and Mock libraries, along with current web development techniques. This book - updated for Python 3.11 and Django 4 - clearly demonstrates how TDD encourages simple designs and inspires confidence. My main aim is to impart a methodology - a way of doing web development, which I think makes for better web apps and happier developers. There's not much point in a book that just covers material you could find by Googling, so this book isn't a guide to Python syntax, or a tutorial on web development per se. Instead, I hope to teach you how to use TDD to get more reliably to our shared, holy goal: clean code that works.