Book Image

Learning Python Design Patterns - Second Edition - Second Edition

By : Chetan Giridhar, Gennadiy Zlobin
Book Image

Learning Python Design Patterns - Second Edition - Second Edition

By: Chetan Giridhar, Gennadiy Zlobin

Overview of this book

With the increasing focus on optimized software architecture and design it is important that software architects think about optimizations in object creation, code structure, and interaction between objects at the architecture or design level. This makes sure that the cost of software maintenance is low and code can be easily reused or is adaptable to change. The key to this is reusability and low maintenance in design patterns. Building on the success of the previous edition, Learning Python Design Patterns, Second Edition will help you implement real-world scenarios with Python’s latest release, Python v3.5. We start by introducing design patterns from the Python perspective. As you progress through the book, you will learn about Singleton patterns, Factory patterns, and Façade patterns in detail. After this, we’ll look at how to control object access with proxy patterns. It also covers observer patterns, command patterns, and compound patterns. By the end of the book, you will have enhanced your professional abilities in software architecture, design, and development.
Table of Contents (19 chapters)
Learning Python Design Patterns Second Edition
Credits
Foreword
About the Author
About the Reviewer
www.PacktPub.com
Preface
Index

Introducing the Command pattern


As we saw in the previous chapter, Behavioral patterns focus on the responsibilities that an object has. It deals with the interaction among objects to achieve larger functionality. The Command pattern is a behavioral design pattern in which an object is used to encapsulate all the information needed to perform an action or trigger an event at a later time. This information includes the following:

  • The method name

  • An object that owns the method

  • Values for method parameters

Let's understand the pattern with a very simple software example. Consider the case of an installation wizard. A typical wizard may contain multiple phases or screens that capture a user's preferences. While the user browses through the wizard, s/he makes certain choices. Wizards are typically implemented with the Command pattern. A wizard is first launched with an object called the Command object. The preferences or choices made by the user in multiple phases of the wizard are then stored in...