Python Cookbook

Chapter 5. Object-Oriented Programming

Introduction

Credit: Alex Martelli, AB Strakt, author of forthcoming Python in a Nutshell

Object-oriented programming (OOP) is among Python’s greatest strengths. Python’s OOP features keep improving steadily and gradually, just like Python in general. You could write object-oriented programs better in Python 1.5.2 (the ancient, long-stable version that was new when I first began to work with Python) than in any other popular language (excluding, of course, Lisp and its variants—I doubt there’s anything you can’t do well in Lisp-like languages, as long as you can stomach the parentheses-heavy concrete syntax). Now, with Python 2.2, OOP is substantially better than with 1.5.2. I am constantly amazed at the systematic progress Python achieves without sacrificing solidity, stability, and backward compatibility.

To get the most out of Python’s OOP features, you should use them “the Python way,” rather than trying to mimic C++, Java, Smalltalk, or other languages you may be familiar with. You can do a lot of mimicry, but you’ll get better mileage if you invest in understanding the Python way. Most of the investment is in increasing your understanding of OOP itself: what does OOP buy you, and which underlying mechanisms can your object-oriented programs use? The rest of the investment is in understanding the specific mechanisms that Python itself offers.

One caveat is in order. For such a high-level language, Python is quite explicit about the OOP mechanisms ...