David Beazley is an independent software developer and book author living in the city of Chicago. He primarily works on programming tools, provide custom software development, and teach practical programming courses for software developers, scientists, and engineers. He is best known for his work with the Python programming language, for which he has created several open-source packages (e.g., Swig and PLY) and authored the acclaimed Python Essential Reference. He also has significant experience with systems programming in C, C++, and assembly language. Brian K. Jones is a system administrator in the department of computer science at Princeton University.