Book Image

Python: Master the Art of Design Patterns

Book Image

Python: Master the Art of Design Patterns

Overview of this book

Python is an object-oriented scripting language that is used in everything from data science to web development. Known for its simplicity, Python increases productivity and minimizes development time. Through applying essential software engineering design patterns to Python, Python code becomes even more efficient and reusable from project to project. This learning path takes you through every traditional and advanced design pattern best applied to Python code, building your skills in writing exceptional Python. Divided into three distinct modules, you’ll go from foundational to advanced concepts by following a series of practical tutorials. Start with the bedrock of Python programming – the object-oriented paradigm. Rethink the way you work with Python as you work through the Python data structures and object-oriented techniques essential to modern Python programming. Build your confidence as you learn Python syntax, and how to use OOP principles with Python tools such as Django and Kivy. In the second module, run through the most common and most useful design patterns from a Python perspective. Progress through Singleton patterns, Factory patterns, Façade patterns and more all with detailed hands-on guidance. Enhance your professional abilities in in software architecture, design, and development. In the final module, run through the more complex and less common design patterns, discovering how to apply them to Python coding with the help of real-world examples. Get to grips with the best practices of writing Python, as well as creating systems architecture and troubleshooting issues. This Learning Path combines some of the best that Packt has to offer in one complete, curated package. It includes content from the following Packt products: ? Python 3 Object-Oriented Programming - Second Edition by Dusty Phillips ? Learning Python Design Patterns - Second Edition by Chetan Giridhar ? Mastering Python Design Patterns by Sakis Kasampalis
Table of Contents (6 chapters)
4
A. Bibliography
5
Index

Chapter 5. The Decorator Pattern

Whenever we want to add extra functionality to an object, we have a number of different options. We can:

  • Add the functionality directly to the class the object belongs to, if it makes sense (for example, add a new method)
  • Use composition
  • Use inheritance

Composition should generally be preferred over inheritance, because inheritance makes code reuse harder, it's static, and applies to an entire class and all instances of it [GOF95, page 31], [j.mp/decopat].

Design patterns offer us a fourth option that supports extending the functionality of an object dynamically (in runtime): Decorators. A Decorator pattern can add responsibilities to an object dynamically, and in a transparent manner (without affecting other objects) [GOF95, page 196].

In many programming languages, the Decorator pattern is implemented using sub-classing (inheritance) [GOF95, page 198]. In Python, we can (and should) use the built-in decorator feature. A Python decorator is a specific...