Learning Python, 6th Edition

Chapter 23. Module Coding Basics

Now that we’ve studied the larger ideas behind modules, let’s turn to some examples of modules in action. Although some of the early topics in this chapter will be review for linear readers who have already applied them in previous chapters’ demos, even simple modules can quickly lead us to further details that we haven’t yet encountered in full, such as nesting, reloads, scopes, and more, which we’ll pick up here.

In general, Python modules are easy to create; they’re just files of Python program code created with a text editor, and require no special syntax. Because Python does all the work of finding and loading modules, they are also easy to use; simply import a module or its names, and use the objects they reference. Let’s explore both sides of this fence.

Creating Modules

To define a module, simply use your text editor to type Python code into a text file, and save it with a .py extension; any such file is automatically considered a Python module. As we’ve seen, all the names assigned at the top level of the module become its attributes (names associated with the module object) and are exported for clients to use—they morph from variable to module object attribute automatically.

For instance, if you type the code in Example 23-1 into a file called module1.py and import it, you create a module object with one attribute—the name printer, which happens to be a reference to a function object.

Example 23-1. module1.py

def printer(x):           # Module ...