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- Herausgeber: Packt Publishing
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
Introducing modular techniques for building sophisticated programs using Python
About This Book
- The book would help you develop succinct, expressive programs using modular deign
- The book would explain best practices and common idioms through carefully explained and structured examples
- It will have broad appeal as far as target audience is concerned and there would be take away for all beginners to Python
Who This Book Is For
This book is intended for beginner to intermediate level Python programmers who wish to learn how to use modules and packages within their programs. While readers must understand the basics of Python programming, no knowledge of modular programming techniques is required.
What You Will Learn
- Learn how to use modules and packages to organize your Python code
- Understand how to use the import statement to load modules and packages into your program
- Use common module patterns such as abstraction and encapsulation to write better programs
- Discover how to create self-testing Python packages
- Create reusable modules that other programmers can use
- Learn how to use GitHub and the Python Package Index to share your code with other people
- Make use of modules and packages that others have written
- Use modular techniques to build robust systems that can handle complexity and changing requirements over time
In Detail
Python has evolved over the years and has become the primary choice of developers in various fields. The purpose of this book is to help readers develop readable, reliable, and maintainable programs in Python.
Starting with an introduction to the concept of modules and packages, this book shows how you can use these building blocks to organize a complex program into logical parts and make sure those parts are working correctly together.
Using clearly written, real-world examples, this book demonstrates how you can use modular techniques to build better programs. A number of common modular programming patterns are covered, including divide-and-conquer, abstraction, encapsulation, wrappers and extensibility. You will also learn how to test your modules and packages, how to prepare your code for sharing with other people, and how to publish your modules and packages on GitHub and the Python Package Index so that other people can use them. Finally, you will learn how to use modular design techniques to be a more effective programmer.
Style and approach
This book will be simple and straightforward, focusing on imparting learning through a wide array of examples that the readers can put into use as they read through the book. They should not only be able to understand the way modules help in improving development, but they should also be able to improvise on their techniques of writing concise and effective code.
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Seitenzahl: 316
Veröffentlichungsjahr: 2016
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Table of Contents
Modular Programming with Python
Modular Programming with Python
Copyright © 2016 Packt Publishing
All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.
Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the author, nor Packt Publishing, and its dealers and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this book.
Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information.
First published: May 2016
Production reference: 1200516
Published by Packt Publishing Ltd.
Livery Place
35 Livery Street
Birmingham B3 2PB, UK.
ISBN 978-1-78588-448-1
www.packtpub.com
Credits
Author
Erik Westra
Reviewer
Mike Driscoll
Commissioning Editor
Priya Singh
Acquisition Editor
Dharmesh Parmar
Content Development Editor
Arun Nadar
Technical Editor
Rupali Shrawane
Copy Editor
Sonia Cheema
Project Coordinator
Nikhil Nair
Proofreader
Safis Editing
Indexer
Hemangini Bari
Graphics
Disha Haria
Production Coordinator
Arvindkumar Gupta
Cover Work
Arvindkumar Gupta
About the Author
Erik Westra has been a professional software developer for over 25 years, and has worked almost exclusively in Python for the past decade. Erik's early interest in graphical user interface design led to the development of one of the most advanced urgent courier dispatch systems used by messenger and courier companies worldwide. In recent years, Erik has been involved in the design and implementation of systems matching seekers and providers of goods and services across a range of geographical areas, as well as real-time messaging and payments systems. This work has included the creation of real-time geocoders and map-based views of constantly changing data. Erik is based in New Zealand, and works for companies worldwide.
Erik is also the author of the Packt titles Python Geospatial Development, Python Geospatial Analysis, and Building Mapping Applications with QGIS.
I would like to thank Ruth for being so awesome, and my children for their patience. Without you, none of this would have been possible.
About the Reviewer
Mike Driscoll has been programming in Python since 2006. He enjoys writing about Python on his blog at http://www.blog.pythonlibrary.org/. He co-authored the Core Python Refcard for DZone. Mike has also been a technical reviewer for Python 3 Object Oriented Programming, Python 2.6 Graphics Cookbook, Tkinter GUI Application Development Hotshot, and several others. He recently wrote the book Python 101, and is working on his next book.
I would like to thank my beautiful wife, Evangeline, for always supporting me. I would also like to thank friends and family for all that they do to help me. And I would like to thank Jesus Christ for saving me.
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Preface
Modular programming is a way of organizing your program's source code. By organizing your code into modules (Python source files) and packages (collections of modules), and then importing those modules and packages into your program, you can keep your programs logically organized and keep potential problems to a minimum.
As your program grows and changes, you will often have to rewrite or expand certain parts of your code. Modular programming techniques help to manage these changes, minimizing side-effects, and keeping your code under control.
As you work with modular programming techniques, you will learn a number of common patterns for using modules and packages, including the divide and conquer approach to programming, the use of abstraction and encapsulation, and the idea of writing extensible modules.
Modular programming techniques are also a great way of sharing your code, either by making it available for other people to use or by reusing your code in another program. Using popular tools such as GitHub and the Python Package Index, you will learn how to publish your code, as well as use code written by other people.
Putting all these techniques together, you will learn how apply "modular thinking" to create better programs. You will see how modules can be used to deal with complexity and change in a large program and how modular programming really is the foundation of good programming technique.
By the end of the book, you will have an excellent understanding of how modules and packages work in Python and how to use them to create high-quality and robust software that can be shared with others.
What this book covers
Chapter 1, Introducing Modular Programming, looks at the ways you can use Python modules and packages to help organize your programs, why it is important to use modular techniques, and how modular programming helps you to deal with the ongoing process of programming.
Chapter 2, Writing Your First Modular Program, introduces the divide and conquer approach to programming and applies this technique to the process of building an inventory control system based on modular programming principles.
Chapter 3, Using Modules and Packages, covers the nuts and bolts of modular programming using Python, including nested packages, package and module initialization techniques, relative imports, choosing what gets imported, and how to deal with circular references.
Chapter 4, Using Modules for Real-World Programming, uses the implementation of a chart-generation library to show how modular techniques help to deal with changing requirements in the best possible way.
Chapter 5, Working with Module Patterns, looks at a number of standard patterns for working with modules and packages, including the divide and conquer technique, abstraction, encapsulation, wrappers, and how to write extensible modules using dynamic imports, plugins, and hooks.
Chapter 6, Creating Reusable Modules, shows how to design and create modules and packages that are intended to be shared with other people.
Chapter 7, Advanced Module Techniques, looks at some of the more distinctive aspects of modular programming in Python, including optional and local imports, tweaking the module search path, "gotchas" to be aware of, how to use modules and packages for rapid application development, working with package globals, package configuration, and package data files.
Chapter 8, Testing and Deploying Modules, examines the concept of unit testing, how to prepare your modules and packages for publication, how to upload and publish your work, and how to make use of modules and packages written by other people.
Chapter 9, Modular Programming as a Foundation for Good Programming Technique, shows how modular techniques help to deal with the ongoing process of programming by dealing with change and managing complexity, and how modular programming techniques help you to be a more effective programmer.
What you need for this book
All you need to follow through the examples in this book is a computer running any recent version of Python. While the examples all use Python 3, they can easily be adapted to work with Python 2 only a few changes.
Who this book is for
This book is aimed at the beginner to intermediate level Python programmer who wishes to use modular programming techniques to create high-quality and well organized programs. While the reader must know the basics of Python, no prior knowledge of modular programming is required.
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Questions
If you have a problem with any aspect of this book, you can contact us at <[email protected]>, and we will do our best to address the problem.
Introducing Python packages
In the same way that Python modules allow you to organize your functions and classes into separate Python source files, Python packages allow you to group multiple modules together.
A Python package is a directory with certain characteristics. For example, consider the following directory of Python source files:
This Python package, called animals, contains five Python modules: cat, cow, dog, horse, and sheep. There is also a special file with the rather unusual name __init__.py. This file is called a package initialization file; the presence of this file tells the Python system that this directory contains a package. The package initialization file can also be used to initialize the package (hence the name) and can also be used to make importing the package easier.
Note
Starting with Python version 3.3, packages don't always need to include an initialization file. However, packages without an initialization file (called namespace packages) are still quite uncommon and are only used in very specific circumstances. To keep things simple, we will be using regular packages (with the __init__.py file) throughout this book.
Just like we used the module name when calling a function within a module, we use the package name when referring to a module within a package. For example, consider the following code:
In this example, the speak() function is defined within the cow.py module, which itself is part of the animals package.
Packages are a great way of organizing more complicated Python programs. You can use them to group related modules together, and you can even define packages inside packages (called nested packages) to keep your program super-organized.
Note that the import statement (and the related from...import statement) can be used in a variety of ways to load packages and modules into your program. We have only scratched the surface here, showing you what modules and packages look like in Python so that you can recognize them when you see them in a program. We will be looking at the way modules and packages can be defined and imported in much more depth in Chapter 3, Using Modules and Packages.
Tip
Downloading the example code
The code bundle for the book is also hosted on GitHub at https://github.com/PacktPublishing/Modular-Programming-with-Python. We also have other code bundles from our rich catalog of books and videos available at https://github.com/PacktPublishing/. Check them out!
Using modules and packages to organize a program
Modules and packages aren't just there to spread your Python code across multiple source files and directories—they allow you to organize your code to reflect the logical structure of what your program is trying to do. For example, imagine that you have been asked to create a web application to store and report on university examination results. Thinking about the business requirements that you have been given, you come up with the following overall structure for your application:
The program is broken into two main parts: a web interface, which interacts with the user (and with other computer programs via an API), and a backend, which handles the internal logic of storing information in a database, generating reports, and e-mailing results to students. As you can see, the web interface itself has been broken down into four parts:
As you consider each logical component of your application (that is, each of the boxes in the preceding illustration), you are also starting to think about the functionality that each component will provide. As you do this, you are already thinking in modular terms. Indeed, each of the logical components of your application can be directly implemented as a Python module or package. For example, you might choose to break your program into two main packages named web and backend, where:
As you can see, each shaded box in the preceding illustration becomes a Python module, and each of the groupings of boxes becomes a Python package.
Once you have decided on the collection of packages and modules that you want to define, you can start to implement each component by writing the appropriate set of functions within each module. For example, the backend.database module might have a function named get_students_results(), which returns a single student's exam results for a given subject and year.
Note
In a real web application, your modular structure may actually be somewhat different. This is because you typically create a web application using a web application framework such as Django, which imposes its own structure on your program. However, in this example we are keeping the modular structure as simple as possible to show how business functionality translates directly into packages and modules.
Obviously, this example is fictitious, but it shows how you can think about a complex program in modular terms, breaking it down into individual components and then using Python modules and packages to implement each of these components in turn.
