Preface By Jeff Elkner This book owes its existence to the collaboration made possible by the Internet and the free software movement.Its three authors-a college professor,a high school teacher,and a professional programmer-have yet to meet face to face, but we have been able to work closely together and have been aided by many wonderful folks who have donated their time and energy to helping make this book better. We think this book is a testament to the benefits and future possibilities of this kind of collaboration,the framework for which has been put in place by Richard Stallman and the Free Software Foundation. How and why I came to use Python In 1999,the College Board's Advanced Placement (AP)Computer Science exam was given in C+for the first time.As in many high schools throughout the country,the decision to change languages had a direct impact on the computer science curriculum at Yorktown High School in Arlington,Virginia,where I teach. Up to this point,Pascal was the language of instruction in both our first-year and AP courses.In keeping with past practice of giving students two years of exposure to the same language,we made the decision to switch to C++in the first-year course for the 1997-98 school year so that we would be in step with the College Board's change for the AP course the following year. Two years later,I was convinced that C++was a poor choice to use for introducing students to computer science.While it is certainly a very powerful programming language,it is also an extremely difficult language to learn and teach.I found myself constantly fighting with C++'s difficult syntax and multiple ways of doing things,and I was losing many students unnecessarily as a result.Convinced therePreface By Jeff Elkner This book owes its existence to the collaboration made possible by the Internet and the free software movement. Its three authors—a college professor, a high school teacher, and a professional programmer—have yet to meet face to face, but we have been able to work closely together and have been aided by many wonderful folks who have donated their time and energy to helping make this book better. We think this book is a testament to the benefits and future possibilities of this kind of collaboration, the framework for which has been put in place by Richard Stallman and the Free Software Foundation. How and why I came to use Python In 1999, the College Board’s Advanced Placement (AP) Computer Science exam was given in C++ for the first time. As in many high schools throughout the country, the decision to change languages had a direct impact on the computer science curriculum at Yorktown High School in Arlington, Virginia, where I teach. Up to this point, Pascal was the language of instruction in both our first-year and AP courses. In keeping with past practice of giving students two years of exposure to the same language, we made the decision to switch to C++ in the first-year course for the 1997-98 school year so that we would be in step with the College Board’s change for the AP course the following year. Two years later, I was convinced that C++ was a poor choice to use for introducing students to computer science. While it is certainly a very powerful programming language, it is also an extremely difficult language to learn and teach. I found myself constantly fighting with C++’s difficult syntax and multiple ways of doing things, and I was losing many students unnecessarily as a result. Convinced there