Book Image

Mastering Python Design Patterns - Second Edition

By : Kamon Ayeva, Sakis Kasampalis
Book Image

Mastering Python Design Patterns - Second Edition

By: Kamon Ayeva, Sakis Kasampalis

Overview of this book

Python is an object-oriented scripting language that is used in a wide range of categories. In software engineering, a design pattern is an elected solution for solving software design problems. Although they have been around for a while, design patterns remain one of the top topics in software engineering, and are a ready source for software developers to solve the problems they face on a regular basis. This book takes you through a variety of design patterns and explains them with real-world examples. You will get to grips with low-level details and concepts that show you how to write Python code, without focusing on common solutions as enabled in Java and C++. You'll also fnd sections on corrections, best practices, system architecture, and its designing aspects. This book will help you learn the core concepts of design patterns and the way they can be used to resolve software design problems. You'll focus on most of the Gang of Four (GoF) design patterns, which are used to solve everyday problems, and take your skills to the next level with reactive and functional patterns that help you build resilient, scalable, and robust applications. By the end of the book, you'll be able to effciently address commonly faced problems and develop applications, and also be comfortable working on scalable and maintainable projects of any size.
Table of Contents (17 chapters)

Implementation

There are many ways to implement a Chain of Responsibility in Python, but my favorite implementation is the one by Vespe Savikko (https://legacy.python.org/workshops/1997-10/proceedings/savikko.html). Vespe's implementation uses dynamic dispatching in a Pythonic style to handle requests (http://j.mp/ddispatch).

Let's implement a simple, event-based system using Vespe's implementation as a guide. The following is the UML class diagram of the system:

The Event class describes an event. We'll keep it simple, so in our case, an event has only a name:

class Event:
def __init__(self, name):
self.name = name

def __str__(self):
return self.name

The Widget class is the core class of the application. The parent aggregation shown in the UML diagram indicates that each widget can have a reference to a parent object, which by convention...