Think Python - UW Faculty Web Server

PrefaceThe strange history of this bookIn 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 ratein the class was too high and, even for
students who succeeded, the overall level of achievement was too low.
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 myown book. My goals were:
• Keep it short. It is better for students to read 10 pages thannot 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 choseHow 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.
IreleasedthebookundertheGNUFreeDocumentationLicense, whichallowsuserstocopy, modify,
and distribute the book.
What happened next is the cool part. Jeff Elkner, a high schoolteacher 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 Doc-
umentation License. As Green Tea Press, I published the bookand started selling hard copies
through Amazon.com and college book stores. Other books from Green Tea Press are available at
greenteapress.com.
viChapter 0. Preface
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. In2008 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!
The result is this book, now with the less grandiose titleThink Python. Some of the changes are:
• I added a section about debugging at the end of each chapter.These sections present general
techniques for finding and avoiding bugs, and warnings aboutPython pitfalls.
• I removed the material in the last few chapters about the implementation of lists and trees. I
still love those topics, but I thought they were incongruentwith the rest of the book.
• I added more exercises, ranging from short tests of understanding to a few substantial projects.
• I added a series of case studies—longer examples with exercises, solutions, and discussion.
Some of them are based on Swampy, a suite of Python programs I wrote for use in my classes.
Swampy, code examples, and some solutions are available from
thinkpython.com.
• I expanded the discussion of program development plans andbasic design patterns.
• The use of Python is more idiomatic. The book is still about programming, not Python, but
now I think the book gets more leverage from the language.
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.