Book Image

Secret Recipes of the Python Ninja

Book Image

Secret Recipes of the Python Ninja

Overview of this book

This book covers the unexplored secrets of Python, delve into its depths, and uncover its mysteries. You’ll unearth secrets related to the implementation of the standard library, by looking at how modules actually work. You’ll understand the implementation of collections, decimals, and fraction modules. If you haven’t used decorators, coroutines, and generator functions much before, as you make your way through the recipes, you’ll learn what you’ve been missing out on. We’ll cover internal special methods in detail, so you understand what they are and how they can be used to improve the engineering decisions you make. Next, you’ll explore the CPython interpreter, which is a treasure trove of secret hacks that not many programmers are aware of. We’ll take you through the depths of the PyPy project, where you’ll come across several exciting ways that you can improve speed and concurrency. Finally, we’ll take time to explore the PEPs of the latest versions to discover some interesting hacks.
Table of Contents (17 chapters)
Title Page
Copyright and Credits
Packt Upsell
Foreword
Contributors
Preface
Index

Implementing UserList


This wrapper is similar to UserDict, except it applies to lists rather than dictionaries. Its main use is for creating a base class for list-like subclasses that allow for inheritance and method overriding or new methods. This allows for new functionality within lists.

Again, like UserDict, UserList has been largely superseded by the ability to subclass directly from list. But, again, it may be easier to use UserList than a list subclass. While UserList has the methods and capabilities of normal lists, it adds the data attribute to hold the underlying list object contents.

How to do it...

  1. userlist_import.py shows how to use UserList as a superclass for a new list-like object. In this case, we are going to create a class that allows a list to be added by simply assigning values to it, rather than having to call the append() function:

    • First, in line 11, UserList must be imported from the collections module.
    • Next, the ExtendList class is created in line 12 as a subclass of...