Learning Python, 5th Edition

Chapter 23. Module Coding Basics

Now that we’ve looked at 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’ examples, we’ll find that they quickly lead us to further details surrounding Python’s modules that we haven’t yet met, such as nesting, reloads, scopes, and more.

Python modules are easy to create; they’re just files of Python program code created with a text editor. You don’t need to write special syntax to tell Python you’re making a module; almost any text file will do. Because Python handles all the details of finding and loading modules, modules are also easy to use; clients simply import a module, or specific names a module defines, and use the objects they reference.

Module Creation

To define a module, simply use your text editor to type some Python code into a text file, and save it with a “.py” extension; any such file is automatically considered a Python module. 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 following def 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:

def printer(x):                   # Module ...