Book Image

Modular Programming with Python

By : Erik Westra
Book Image

Modular Programming with Python

By: Erik Westra

Overview of this book

Python has evolved over the years and has become the primary choice of developers in various fields. The purpose of this book is to help readers develop readable, reliable, and maintainable programs in Python. Starting with an introduction to the concept of modules and packages, this book shows how you can use these building blocks to organize a complex program into logical parts and make sure those parts are working correctly together. Using clearly written, real-world examples, this book demonstrates how you can use modular techniques to build better programs. A number of common modular programming patterns are covered, including divide-and-conquer, abstraction, encapsulation, wrappers and extensibility. You will also learn how to test your modules and packages, how to prepare your code for sharing with other people, and how to publish your modules and packages on GitHub and the Python Package Index so that other people can use them. Finally, you will learn how to use modular design techniques to be a more effective programmer.
Table of Contents (16 chapters)
Modular Programming with Python
About the Author
About the Reviewer

Refactoring the code

We'll start our refactoring by moving the existing PNG renderers into a new sub-package called renderers.png. Create a new directory named png within the renderers directory, and move the,,, and modules into this directory. Then, create an empty package initialization file,, inside the png directory so that Python will recognize it as a package.

There is one minor change we are going to have to make to our existing PNG renderers: because each renderer module imports the module using a relative import, we will need to update these modules so that they can still find the constants module from their new position. To do this, edit each PNG renderer module in turn, and find the line that looks like the following:

from ..constants import *

Add an extra . to each of these lines so that they look like this:

from ...constants import *

Our next task is to create a package to hold our PDF-format renderers...