Programming Python, 3rd Edition

“The os.path to Knowledge”

This chapter begins our in-depth look at ways to apply Python to real programming tasks. In this and the following chapters, you’ll see how to use Python to write system tools, GUIs, database applications, Internet scripts, web sites, and more. Along the way, we’ll also study larger Python programming concepts in action: code reuse, maintainability, object-oriented programming (OOP), and so on.

In this first part of the book, we begin our Python programming tour by exploring the systems application domain— scripts that deal with files, programs, and the general environment surrounding a program. Although the examples in this domain focus on particular kinds of tasks, the techniques they employ will prove to be useful in later parts of the book as well. In other words, you should begin your journey here, unless you are already a Python systems programming wizard.

Why Python Here?

Python’s system interfaces span application domains, but for the next five chapters, most of our examples fall into the category of system tools—programs sometimes called command-line utilities, shell scripts, and other permutations of such words. Regardless of their title, you are probably already familiar with this sort of script; these scripts accomplish such tasks as processing files in a directory, launching test scripts, and so on. Such programs historically have been written in nonportable and syntactically obscure shell languages such as DOS batch files, csh, and awk.

Even ...