A First Script

Let’s get started. Open your favorite text editor (e.g., vi, Notepad, or the IDLE editor), and type the following statements into a new text file named script1.py:

# A first Python script
import sys                  # Load a library module
print(sys.platform)
print(2 ** 100)             # Raise 2 to a power
x = 'Spam!'
print(x * 8)                # String repetition

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This file is our first official Python script (not counting the two-liner in Chapter 2). You shouldn’t worry too much about this file’s code, but as a brief description, this file:

 

 
  • Imports a Python module (libraries of additional tools), to fetch the name of the platform
  • Runs three print function calls, to display the script’s results
  • Uses a variable named x, created when it’s assigned, to hold onto a string object
  • Applies various object operations that we’ll begin studying in the next chapter

The sys.platform here is just a string that identifies the kind of computer you’re working on; it lives in a standard Python module called sys, which you must import to load (again, more on imports later).

For color, I’ve also added some formal Python comments here—the text after the # characters. Comments can show up on lines by themselves, or to the right of code on a line. The text after a # is simply ignored as a human-readable comment and is not considered part of the statement’s syntax. If you’re copying this code, you can ignore the comments as well. In this book, we usually use a different formatting style to make comments more visually distinctive, but they’ll appear as normal text in your code.

Again, don’t focus on the syntax of the code in this file for now; we’ll learn about all of it later. The main point to notice is that you’ve typed this code into a file, rather than at the interactive prompt. In the process, you’ve coded a fully functional Python script.

Notice that the module file is called script1.py. As for all top-level files, it could also be called simply script, but files of code you want to import into a client have to end with a .py suffix. We’ll study imports later in this chapter. Because you may want to import them in the future, it’s a good idea to use .py suffixes for most Python files that you code. Also, some text editors detect Python files by their .py suffix; if the suffix is not present, you may not get features like syntax colorization and automatic indentation.