Preface

The first edition of this book came out on the day of my 40^th birthday. It feels like yesterday, but actually it was 6 years ago. In a few weeks, the book became a top seller, and to this day that translates into lovely messages and emails I get from readers all over the world.

A couple of years later, I wrote a second edition. That turned out to be a better book, which kept growing in sales and popularity.

And now here we are, at the third edition, and this time it won't just be me narrating the story, because for this edition I have been joined by my dear friend and colleague, Heinrich Kruger.

Together, we have reworked the book's structure. We removed what we felt didn't fit anymore, and added what we thought would benefit you the most. We have shuffled things around, amended old chapters, and written new ones. We have made sure that both our contributions and our best ideas are on each page you will read. We are both very happy about this.

I always wanted to work on a project like this with Heinrich, for whom I have felt enormous respect since I got to know him. He has brought to this book his unique perspective, his incredible talent as a software developer, and he's helped me with my English too!

Everything has been updated to Python 3.9, but of course most of the code will still work with any recent version of Python 3. The scary chapter about concurrency is gone, and the one on Web programming has been replaced with another which introduces the concept of APIs. We have also added a whole new chapter about packaging Python applications, which we feel is the perfect way to close the book.

We are confident this edition is much better than the previous ones; it's more mature, it tells a better story, and it will take you places.

One thing I am particularly happy about is that the soul of the book is still the same. This is not just a book about Python. This is, first and foremost, a book about programming. A book that aims to convey to you as much information as possible, and sometimes, for practical reasons, it does so by pointing you to the Web to dig deeper, to investigate further.

It is designed to last. It expresses concepts and information in a way that should stand the test of time, for as long as possible. We have put in a great amount of thinking to achieve that.

And it will require you to work hard. The code is available for you to download, and we do encourage you to play with it, expand it, change it, break it, and see things for yourself. We want you to develop critical thinking. We want you to be independent, empowered.

That is the soul of the book, and our hope is that wherever you are in your journey, it will help you go further, become a better programmer, in any way that is possible.

When we received the drafts from the second edition to start working on the third one, I was surprised to notice I could not find myself in those pages. Those pages have shown me how my thinking, and therefore my writing, has changed, in the past few years.

Change is interwoven in the very fabric of this universe. Everything changes, all the time. So, our wish for you is that you never fixate on opinions, that you never grow stale. Instead, we hope our work, and the way we present it to you, will help you stay flexible, smart, pragmatic, and adaptable.

We wish you good luck! And don't forget to enjoy the ride!