Learning Python, 5th Edition

Chapter 3. How You Run Programs

OK, it’s time to start running some code. Now that you have a handle on the program execution model, you’re finally ready to start some real Python programming. At this point, I’ll assume that you have Python installed on your computer; if you don’t, see the start of the prior chapter and Appendix A for installation and configuration hints on various platforms. Our goal here is to learn how to run Python program code.

There are multiple ways to tell Python to execute the code you type. This chapter discusses all the program launching techniques in common use today. Along the way, you’ll learn how to both type code interactively, and how to save it in files to be run as often as you like in a variety of ways: with system command lines, icon clicks, module imports, exec calls, menu options in the IDLE GUI, and more.

As for the previous chapter, if you have prior programming experience and are anxious to start digging into Python itself, you may want to skim this chapter and move on to Chapter 4. But don’t skip this chapter’s early coverage of preliminaries and conventions, its overview of debugging techniques, or its first look at module imports—a topic essential to understanding Python’s program architecture, which we won’t revisit until a later part. I also encourage you to see the sections on IDLE and other IDEs, so you’ll know what tools are available when you start developing more sophisticated Python programs.

The Interactive Prompt

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