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

The Proxy pattern in the real world


We will take up a payment use case to demonstrate a real-world scenario for the Proxy pattern. Let's say that you go to shop at a mall and like a nice denim shirt there. You would like to purchase the shirt but you don't have enough cash to do so.

In yesteryears, you'd go to an ATM, take out the money, then come to the mall, and pay for it. Even earlier, you had a bank check for which you had to go to the bank, withdraw money, and then come back to pay for your expense.

Thanks to the banks, we now have something called a debit card. So now, when you want to purchase something, you present your debit card to the merchant. When you punch in your card details, the money is debited in the merchant's account for your expense.

Let's develop an application in Python v3.5 and implement the above use case. We start with the client first. You went to the shopping mall and now would like to purchase a nice denim shirt. Lets see how Client code is written:

  • Your behavior...