Portions of this book have long, long lists of past authors and contributors. They have been adapted and updated over many years and many versions. The following includes contributors and prefaces from previous versions from which this book has grown.

Preface for Python for Everybody

Remixing an Open Book

It is quite natural for academics who are continuously told to “publish or perish” to want to always create something from scratch that is their own fresh creation. This book is an experiment in not starting from scratch, but instead “remixing” the book titled Think Python: How to Think Like a Computer Scientist written by Allen B. Downey, Jeff Elkner, and others.

In December of 2009, I was preparing to teach SI502 - Networked Programming at the University of Michigan for the fifth semester in a row and decided it was time to write a Python textbook that focused on exploring data instead of understanding algorithms and abstractions. My goal in SI502 is to teach people lifelong data handling skills using Python. Few of my students were planning to be professional computer programmers. Instead, they planned to be librarians, managers, lawyers, biologists, economists, etc., who happened to want to skillfully use technology in their chosen field.

I never seemed to find the perfect data-oriented Python book for my course, so I set out to write just such a book. Luckily at a faculty meeting three weeks before I was about to start my new book from scratch over the holiday break, Dr. Atul Prakash showed me the Think Python book which he had used to teach his Python course that semester. It is a well-written Computer Science text with a focus on short, direct explanations and ease of learning.

The overall book structure has been changed to get to doing data analysis problems as quickly as possible and have a series of running examples and exercises about data analysis from the very beginning.

Chapters 2–10 are similar to the Think Python book, but there have been major changes. Number-oriented examples and exercises have been replaced with data-oriented exercises. Topics are presented in the order needed to build increasingly sophisticated data analysis solutions. Some topics like try and except are pulled forward and presented as part of the chapter on conditionals. Functions are given very light treatment until they are needed to handle program complexity rather than introduced as an early lesson in abstraction. Nearly all user-defined functions have been removed from the example code and exercises outside of Chapter 4. The word “recursion” 1 does not appear in the book at all.

In chapters 1 and 11–16, all of the material is brand new, focusing on real-world uses and simple examples of Python for data analysis including regular expressions for searching and parsing, automating tasks on your computer, retrieving data across the network, scraping web pages for data, object-oriented programming, using web services, parsing XML and JSON data, creating and using databases using Structured Query Language, and visualizing data.

The ultimate goal of all of these changes is to shift from a Computer Science to an Informatics focus and to only include topics into a first technology class that can be useful even if one chooses not to become a professional programmer.

Students who find this book interesting and want to further explore should look at Allen B. Downey’s Think Python book. Because there is a lot of overlap between the two books, students will quickly pick up skills in the additional areas of technical programming and algorithmic thinking that are covered in Think Python. And given that the books have a similar writing style, they should be able to move quickly through Think Python with a minimum of effort.

As the copyright holder of Think Python, Allen has given me permission to change the book’s license on the material from his book that remains in this book from the GNU Free Documentation License to the more recent Creative Commons Attribution — Share Alike license. This follows a general shift in open documentation licenses moving from the GFDL to the CC-BY-SA (e.g., Wikipedia). Using the CC-BY-SA license maintains the book’s strong copyleft tradition while making it even more straightforward for new authors to reuse this material as they see fit.

I feel that this book serves as an example of why open materials are so important to the future of education, and I want to thank Allen B. Downey and Cambridge University Press for their forward-looking decision to make the book available under an open copyright. I hope they are pleased with the results of my efforts and I hope that you, the reader, are pleased with our collective efforts.

I would like to thank Allen B. Downey and Lauren Cowles for their help, patience, and guidance in dealing with and resolving the copyright issues around this book.

Charles Severance
Ann Arbor, MI, USA
September 9, 2013

Charles Severance is a Clinical Associate Professor at the University of Michigan School of Information.


Except, of course, for this line.

Contributor List for Python for Everybody

Elliott Hauser, Stephen Catto, Sue Blumenberg, Tamara Brunnock, Mihaela Mack, Chris Kolosiwsky, Dustin Farley, Jens Leerssen, Naveen KT, Mirza Ibrahimovic, Naveen (@togarnk), Zhou Fangyi, Alistair Walsh, Erica Brody, Jih-Sheng Huang, Louis Luangkesorn, and Michael Fudge

You can see contribution details at:

Contributor List for Python for Informatics

Bruce Shields for copy editing early drafts, Sarah Hegge, Steven Cherry, Sarah Kathleen Barbarow, Andrea Parker, Radaphat Chongthammakun, Megan Hixon, Kirby Urner, Sarah Kathleen Barbrow, Katie Kujala, Noah Botimer, Emily Alinder, Mark Thompson-Kular, James Perry, Eric Hofer, Eytan Adar, Peter Robinson, Deborah J. Nelson, Jonathan C. Anthony, Eden Rassette, Jeannette Schroeder, Justin Feezell, Chuanqi Li, Gerald Gordinier, Gavin Thomas Strassel, Ryan Clement, Alissa Talley, Caitlin Holman, Yong-Mi Kim, Karen Stover, Cherie Edmonds, Maria Seiferle, Romer Kristi D. Aranas (RK), Grant Boyer, Hedemarrie Dussan,

Preface for “Think Python”

The strange history of “Think Python”

(Allen B. Downey)

In January 1999 I was preparing to teach an introductory programming class in Java. I had taught it three times and I was getting frustrated. The failure rate in the class was too high and, even for students who succeeded, the overall level of achievement was too low.

One of the problems I saw was the books. They were too big, with too much unnecessary detail about Java, and not enough high-level guidance about how to program. And they all suffered from the trap door effect: they would start out easy, proceed gradually, and then somewhere around Chapter 5 the bottom would fall out. The students would get too much new material, too fast, and I would spend the rest of the semester picking up the pieces.

Two weeks before the first day of classes, I decided to write my own book. My goals were:

  • Keep it short. It is better for students to read 10 pages than not read 50 pages.

  • Be careful with vocabulary. I tried to minimize the jargon and define each term at first use.

  • Build gradually. To avoid trap doors, I took the most difficult topics and split them into a series of small steps.

  • Focus on programming, not the programming language. I included the minimum useful subset of Java and left out the rest.

I needed a title, so on a whim I chose How to Think Like a Computer Scientist.

My first version was rough, but it worked. Students did the reading, and they understood enough that I could spend class time on the hard topics, the interesting topics and (most important) letting the students practice.

I released the book under the GNU Free Documentation License, which allows users to copy, modify, and distribute the book.

What happened next is the cool part. Jeff Elkner, a high school teacher in Virginia, adopted my book and translated it into Python. He sent me a copy of his translation, and I had the unusual experience of learning Python by reading my own book.

Jeff and I revised the book, incorporated a case study by Chris Meyers, and in 2001 we released How to Think Like a Computer Scientist: Learning with Python, also under the GNU Free Documentation License. As Green Tea Press, I published the book and started selling hard copies through and college book stores. Other books from Green Tea Press are available at

In 2003 I started teaching at Olin College and I got to teach Python for the first time. The contrast with Java was striking. Students struggled less, learned more, worked on more interesting projects, and generally had a lot more fun.

Over the last five years I have continued to develop the book, correcting errors, improving some of the examples and adding material, especially exercises. In 2008 I started work on a major revision—at the same time, I was contacted by an editor at Cambridge University Press who was interested in publishing the next edition. Good timing!

I hope you enjoy working with this book, and that it helps you learn to program and think, at least a little bit, like a computer scientist.

Acknowledgements for “Think Python”

(Allen B. Downey)

First and most importantly, I thank Jeff Elkner, who translated my Java book into Python, which got this project started and introduced me to what has turned out to be my favorite language.

I also thank Chris Meyers, who contributed several sections to How to Think Like a Computer Scientist.

And I thank the Free Software Foundation for developing the GNU Free Documentation License, which helped make my collaboration with Jeff and Chris possible.

I also thank the editors at Lulu who worked on How to Think Like a Computer Scientist.

I thank all the students who worked with earlier versions of this book and all the contributors (listed in an Appendix) who sent in corrections and suggestions.

And I thank my wife, Lisa, for her work on this book, and Green Tea Press, and everything else, too.

Allen B. Downey
Needham MA

Allen Downey is an Associate Professor of Computer Science at the Franklin W. Olin College of Engineering.

Contributor List for “Think Python”

(Allen B. Downey)

More than 100 sharp-eyed and thoughtful readers have sent in suggestions and corrections over the past few years. Their contributions, and enthusiasm for this project, have been a huge help.

For the detail on the nature of each of the contributions from these individuals, see the “Think Python” text.

Lloyd Hugh Allen, Yvon Boulianne, Fred Bremmer, Jonah Cohen, Michael Conlon, Benoit Girard, Courtney Gleason and Katherine Smith, Lee Harr, James Kaylin, David Kershaw, Eddie Lam, Man-Yong Lee, David Mayo, Chris McAloon, Matthew J. Moelter, Simon Dicon Montford, John Ouzts, Kevin Parks, David Pool, Michael Schmitt, Robin Shaw, Paul Sleigh, Craig T. Snydal, Ian Thomas, Keith Verheyden, Peter Winstanley, Chris Wrobel, Moshe Zadka, Christoph Zwerschke, James Mayer, Hayden McAfee, Angel Arnal, Tauhidul Hoque and Lex Berezhny, Dr. Michele Alzetta, Andy Mitchell, Kalin Harvey, Christopher P. Smith, David Hutchins, Gregor Lingl, Julie Peters, Florin Oprina, D. J. Webre, Ken, Ivo Wever, Curtis Yanko, Ben Logan, Jason Armstrong, Louis Cordier, Brian Cain, Rob Black, Jean-Philippe Rey at Ecole Centrale Paris, Jason Mader at George Washington University made a number Jan Gundtofte-Bruun, Abel David and Alexis Dinno, Charles Thayer, Roger Sperberg, Sam Bull, Andrew Cheung, C. Corey Capel, Alessandra, Wim Champagne, Douglas Wright, Jared Spindor, Lin Peiheng, Ray Hagtvedt, Torsten Hübsch, Inga Petuhhov, Arne Babenhauserheide, Mark E. Casida, Scott Tyler, Gordon Shephard, Andrew Turner, Adam Hobart, Daryl Hammond and Sarah Zimmerman, George Sass, Brian Bingham, Leah Engelbert-Fenton, Joe Funke, Chao-chao Chen, Jeff Paine, Lubos Pintes, Gregg Lind and Abigail Heithoff, Max Hailperin, Chotipat Pornavalai, Stanislaw Antol, Eric Pashman, Miguel Azevedo, Jianhua Liu, Nick King, Martin Zuther, Adam Zimmerman, Ratnakar Tiwari, Anurag Goel, Kelli Kratzer, Mark Griffiths, Roydan Ongie, Patryk Wolowiec, Mark Chonofsky, Russell Coleman, Wei Huang, Karen Barber, Nam Nguyen, Stéphane Morin, Fernando Tardio, and Paul Stoop.