Python Projects E-Book

Laura Cassell

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 630

Veröffentlichungsjahr: 2014

Beschreibung

A guide to completing Python projects for those ready to take their skills to the next level Python Projects is the ultimate resource for the Python programmer with basic skills who is ready to move beyond tutorials and start building projects. The preeminent guide to bridge the gap between learning and doing, this book walks readers through the "where" and "how" of real-world Python programming with practical, actionable instruction. With a focus on real-world functionality, Python Projects details the ways that Python can be used to complete daily tasks and bring efficiency to businesses and individuals alike. Python Projects is written specifically for those who know the Python syntax and lay of the land, but may still be intimidated by larger, more complex projects. The book provides a walk-through of the basic set-up for an application and the building and packaging for a library, and explains in detail the functionalities related to the projects. Topics include: *How to maximize the power of the standard library modules *Where to get third party libraries, and the best practices for utilization *Creating, packaging, and reusing libraries within and across projects *Building multi-layered functionality including networks, data, and user interfaces *Setting up development environments and using virtualenv, pip, and more Written by veteran Python trainers, the book is structured for easy navigation and logical progression that makes it ideal for individual, classroom, or corporate training. For Python developers looking to apply their skills to real-world challenges, Python Projects is a goldmine of information and expert insight.

Leseprobe

Contents

Introduction

Why We Wrote This Book

Who This Book For

What You Will Learn

What You Need to Use This Book

Conventions

Source Code

Errata

p2p.wrox.com

Chapter 1: Reviewing Core Python

Exploring the Python Language and the Interpreter

Reviewing the Python Data Types

Using Python Control Structures

Getting Data In and Out of Python

Extending Python

Creating and Using Modules and Packages

Creating an Example Package

Using Third-Party Packages

Summary

Chapter 2: Scripting with Python

Accessing the Operating System

Working with Dates and Times

Handling Common File Formats

Accessing Native APIs with ctypes and pywin32

Automating Tasks Involving Multiple Applications

Summary

Chapter 3: Managing Data

Storing Data Using Python

Analyzing Data with Python

Managing Data Using SQL

Migrating LendyDB to an SQL Database

Exploring Other Data Management Options

Summary

Chapter 4: Building Desktop Applications

Structuring Applications

Building Command-Line Interfaces

Using the cmd Module to Build a Command-Line Interface

Reading Command-Line Arguments

Jazzing Up the Command-Line Interface with Some Dialogs

Programming GUIs with Tkinter

Storing Local Data

Understanding Localization

Summary

Chapter 5: Python on the Web

Python on the Web

Web Programming with Python

More on Python and the Web

Using Python Across the Wire

More Networking Fun in Python

Summary

Exercises

Chapter 6: Python in Bigger Projects

Testing with the Doctest Module

Testing with the Unittest Module

Test-Driven Development in Python

Debugging Your Python Code

Working on Larger Python Projects

Releasing Python Packages

Summary

Chapter 7: Exploring Python’s Frontiers

Drawing Pictures with Python

Doing Science with Python

Playing Games with Python

Going to the Movies

Integrating with Other Languages

Getting Physical

Building Python

Summary

Appendix A: Answers to Exercises

Appendix B: Python Standard Modules

Appendix C: Useful Python Resources

Asking Questions: Mailing Lists and More

Reading Blogs

Studying Tutorials and References

Watching Videos

And Now for Something Completely Different…

References

Title Page

Copyright

Dedication

About the Authors

About the Technical Editors

Credits

Acknowledgments

Advert

Wiley End User License Agreement

List of Tables

Chapter 1

Table 1.1

Table 1.2

Table 1.3

Table 1.4

Table 1.5

Chapter 2

Table 2.1

Chapter 3

Table 3.1

Table 3.2

Table 3.3

Table 3.4

Table 3.5

Table 3.6

Chapter 4

Table 4.1

List of Illustrations

Chapter 2

Figure 2.1 The toolhire spreadsheet

Chapter 4

Figure 4.1 Module interaction sequence diagram

Figure 4.2 Initial message box screenshot

Figure 4.3 Example of a GUI containment tree

Figure 4.4 demo1.py in action

Figure 4.5 Tic-tac-toe GUI design

Figure 4.6 Final Tkinter GUI

Figure 4.7 A Tix ComboBox

Figure 4.8 A Tix ScrolledText Widget in Action

Figure 4.9 Modifying Text appearance in a text widget

Figure 4.10 Tix Notebook showing two pages

Figure 4.11 Various ttk Themes

Chapter 5

Figure 5.1 Note the two sides of a web app: client-side and server-side. Server-side data is served via a web server such as Apache or Nginx.

Figure 5.2 Structure of a network request

Figure 5.3 The Chrome Developer Tools, illustrating the headers of a server request for a file

Figure 5.4 The DevTools Network tab

Figure 5.5 FigurePreview of the selected file

Figure 5.6 Headers for the selected file

Figure 5.7 The Headers tab in Chrome’s DevTools, illustrating the HTTP response from the USDA website

Figure 5.8 Note how this displays the HTML file we created earlier.

Guide

Cover

Table of Contents

Chapter 1

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Introduction

AFTER A CONFERENCE ONE YEAR, an e-mail went around the PyLadies organizers mailing list asking, “Is anyone interested in writing a Python book?” I had kicked around the idea of a programming book for a while. After teaching for a couple years and mentoring at PyLadies and other coding meetups, I realized there was a need for a new, specific sort of programming book. I didn’t jump to replying to the e-mail, however. I knew that writing a book would be a big process (boy is it!) and that it would take a lot of time and effort on my part, in the way of working on the weekends and holidays (yep, check!). I also knew that I had a full-time job teaching programming, I was the lead organizer for my local PyLadies chapter in Atlanta, Georgia, and I had children that would soon start asking, “Are you writing this weekend?”

All of the above was true (a little more than I originally thought, actually), but I knew that the book was important. There were so many of my students asking me at the end of class, “Now that I know the basics of Python, what do I do?” My answer was always something along the lines of, “You can get involved in open-source projects!” or “Take the advanced Python class!” But none of those answers satisfied them or me. The answer is, “You have to really start looking for something to work on—a problem to solve, a need that must be met.” Because, the only way to really know and understand programming and a programming language is to solve problems with said language.

But then the problem of “But I don’t have a problem that really needs to be solved” cropped up. So while I could send my students off to look at open-source projects that do, in fact, need the help, if they didn’t understand the technology, they’d be lost and give up. Then the community loses yet another programmer who may have brought interesting things to the table. So, that’s when, after lots of talking to friends and family, I realized that this book needed to be written.

Why We Wrote This Book

For all those people who came up to us and asked, over the years, “What can I do now that I understand Python basics? What things can I learn? Where do I go?” That’s why we wrote this book.

The most chronic problem in programming books that we’ve experienced and that others have also felt they experienced is that it goes from “These are the basics of a language” into very deep concepts that only people who hold Computer Science (CS) degrees would understand. And that’s not cool. Programming should be open to anyone who is interested. We should all be working toward making the bar into programming a little lower. We feel that Python accomplishes this, but we need to take it a step further and begin to understand how people learn abstract ideas and concepts, to help us help them learn.

Think of programming like learning how to build a house, but only understanding that wood is needed and how the wood works to build a house. You still need to understand structural engineering, electrical, plumbing, ventilation, HVAC, etc. The same concept is true for programming. Languages just explain the wood being used in a house. There is plenty more that is happening in harmony with the wood, and we want to help you uncover those concepts.

Who This Book For

This book is not for beginners who want to learn Python. Rather, as a reader of this book, you need to already have some Python programming under your belt. That means you’ve done some tutorials. You also understand that whitespace matters in Python and that lists are denoted with hard braces ([ ] ) while dicts (dictionaries) are denoted with curly braces ( { } ). This book is for those people who are still beginners, but who have completed a tutorial or two—folks who understand the basics of Python, but are interested to learn what all they can do with Python.

“Need is the mother of invention” goes the saying, and when you’re learning to program, this is very true. If you need a piece of software that can perform a specific function or task, it’s easy to learn a language around that need. You have a need, the language will help you, you learn the language, you solve the problem, you’ve learned a thing, and you’ve put it to use immediately. This is awesome and fantastic! However, what if you think programming is interesting, but you’re missing the need? What if you don’t know what to make? That’s where this book comes in.

This book will help you to learn the parts of Python that most people don’t think to tell new programmers about. Most of the things covered in this book are tools and technologies that one may only discover when they are faced with working with them. However, for new programmers who don’t have a specific problem to solve, learning these tools can be difficult. Most of the time no one thinks to introduce these topics to programmers because they are used so regularly. We hope to take you on a journey through the power of Python and all of its splendor.

You will learn how to make a web app, how to talk to a database using Python libraries, and which system tools can help speed up your workflow, if you’re a systems administrator. We will briefly touch on topics such as security and best practices. You’ll get an overview of creating graphical user interfaces (GUIs) using Python libraries. We will cover consuming and producing application programming interfaces (APIs) and many other topics that are beneficial to Python programmers.

What You Will Learn

We hope to take you on a small tour of the basics that are available in the Python ecosystem. We’ll introduce you to many concepts that are usually discovered only while working on a problem to solve. While we can’t put everything into the context of problems that you may need to solve in the future, we hope that we can illustrate the powerful features of the Python language and the available packages and technology that are available to you, the new Python programmer.

We will start out with a brief “crash course” in Python, in case you’ve forgotten anything. We’ll go over the basics, and then you can decide if you want to read that chapter in its entirety or not. Next, we go over Python as a scripting language. You’ll get to get your hands dirty, as it were, by writing small scripts to access parts of your system, using Python. This should illustrate the very basic power you have with the language. Third, we’ll start talking about data, which is what programming is all about—manipulating data. You’ll get to dive in and work through some examples using some of the standard libraries that come out of the box with Python. We’ll even discuss databases so that you can get a quick intro into those. We want you to see and touch every part of a system that you may come in contact with.

After the first three chapters, you’ll dive into desktop applications. While these aren’t incredibly popular in Python, it is a feature of the language, and it could be useful down the line in your tenure as a Python programmer. Next, we will step out of the desktop and onto the Internet with Python as a data communicator. You’ll learn all about HTTP and the Web and how websites work under the hood. You’ll even be able to play with producing and consuming APIs. APIs confuse many new programmers; we hope to have removed much of the mystery with this chapter.

In the final chapters, we’ll show more advanced topics in Python, such as how to work with Python in bigger projects, debugging your code, creating testing-harnesses, handling errors, and even creating your own exceptions and exception handlers! Finally, there are appendices for reference while you are going through the book and after, when you’re spreading your Python wings and programming.

It is a lot of information, and it’s like a huge sandbox of tools and ideas to get you started on your journey with the language. We hope that you try things out and research more on your own time with certain concepts and ideas that interest you. We’ve included plenty of hands-on exercises to help you try out the concepts as they are presented, as well as some challenge questions in most chapters to help you exercise your newfound knowledge.

What You Need to Use This Book

In order to get the most out of this book, we recommend you have a modern computer running Python 3.3 or later, a good text editor that you are comfortable using, an Internet connection (for some parts of the book), and a healthy dose of patience and wonderment. We also recommend that you utilize Internet searching for any problems that may arise. Professional programmers don’t actually know it all; they usually only know those problems that they deal with day in and day out. A lot of the time of a professional programmer is spent researching and tracking down why a behavior is occurring. No one should ever feel bad for relying on a Google search to solve a problem. Sometimes, your Googling abilities are just as important as your programming ones.

To work through the examples and projects in this book, you will also need the source code. The source code for the samples is available for download from the Wrox website at:

www.wrox.com/go/pythonprojects

Conventions

To help you get the most from the text and keep track of what’s happening, we’ve used a number of conventions throughout the book.

TRY IT OUT

The Try It Out is an exercise you should work through, following the text in the book.

They usually consist of a set of steps.

Each step has a number.

Follow the steps through with your copy of the database.

How It Works

After each Try It Out, the code you’ve typed will be explained in detail.

WARNING Warnings hold important, not-to-be-forgotten information that is directly relevant to the surrounding text.

NOTE Notes indicate notes, tips, hints, tricks, or asides to the current discussion.

As for styles in the text:

We highlight new terms and important words when we introduce them.

We show keyboard strokes like this: Ctrl+A.

We show filenames, URLs, and code within the text like so:

persistence.properties

.

We present code in two different ways:

  We use a monofont type with no highlighting for most code examples.

  We use bold to emphasize code that is particularly important in the present   context or to show changes from a previous code snippet.

Source Code

As you work through the examples in this book, you may choose either to type in all the code manually, or to use the source code files that accompany the book. All the source code used in this book is available for download at www.wrox.com. Specifically for this book, the code download is on the Download Code tab at:

www.wrox.com/go/pythonprojects

You can also search for the book at www.wrox.com by ISBN (the ISBN for this book is 978-1-118-90866-2 to find the code. And a complete list of code downloads for all current Wrox books is available at www.wrox.com/dynamic/books/download.aspx.

Most of the code on www.wrox.com is compressed in a .ZIP, .RAR archive, or similar archive format appropriate to the platform. Once you download the code, just decompress it with an appropriate compression tool.

Errata

We make every effort to ensure that there are no errors in the text or in the code. However, no one is perfect, and mistakes do occur. If you find an error in one of our books, like a spelling mistake or faulty piece of code, we would be very grateful for your feedback. By sending in errata, you may save another reader hours of frustration, and at the same time, you will be helping us provide even higher quality information.

To find the errata page for this book, go to:

www.wrox.com/go/pythonprojects

And click the Errata link. On this page you can view all errata that has been submitted for this book and posted by Wrox editors.

If you don’t spot “your” error on the Book Errata page, go to www.wrox.com/contact/techsupport.shtml and complete the form there to send us the error you have found. We’ll check the information and, if appropriate, post a message to the book’s errata page and fix the problem in subsequent editions of the book.

p2p.wrox.com

For author and peer discussion, join the P2P forums at http://p2p.wrox.com. The forums are a Web-based system for you to post messages relating to Wrox books and related technologies and interact with other readers and technology users. The forums offer a subscription feature to e-mail you topics of interest of your choosing when new posts are made to the forums. Wrox authors, editors, other industry experts, and your fellow readers are present on these forums.

At http://p2p.wrox.com, you will find a number of different forums that will help you, not only as you read this book, but also as you develop your own applications. To join the forums, just follow these steps:

Go to

http://p2p.wrox.com

and click the Register link.

Read the terms of use and click Agree.

Complete the required information to join, as well as any optional information you wish to provide, and click Submit.

You will receive an e-mail with information describing how to verify your account and complete the joining process.

NOTE

You can read messages in the forums without joining P2P, but in order to post your own messages, you must join.

Once you join, you can post new messages and respond to messages other users post. You can read messages at any time on the Web. If you would like to have new messages from a particular forum e-mailed to you, click the Subscribe to this Forum icon by the forum name in the forum listing.

For more information about how to use the Wrox P2P, be sure to read the P2P FAQs for answers to questions about how the forum software works, as well as many common questions specific to P2P and Wrox books. To read the FAQs, click the FAQ link on any P2P page.

1Reviewing Core Python

WHAT YOU WILL LEARN IN THIS CHAPTER:    

The basic features of the Python language

How to use the Python module mechanism

How to create a new module

How to create a new package

WROX.COM CODE DOWNLOADS FOR THIS CHAPTER

You can find the wrox.com downloads for this chapter at www.wrox.com/go/pythonprojects on the Download Code tab. The code is in the Chapter 1 download and individually named according to the names throughout the chapter.

This chapter starts with a brief review of Python—in case you have forgotten some of the basics—and provides a foundation upon which the rest of the book is built. If you are confident in your ability with basic Python coding, feel free to skip ahead until you see content that might be of interest to you. After all, you can always come back to this chapter later if you find you need a refresher.

In this chapter you start off by looking at the Python ecosystem, the data types, and the major control structures and then move on to defining functions and classes. Next, you look at the Python module and package system. And, finally, you create a basic new package of modules.

By the end of this chapter, you should be ready to take the next step and start working with the standard Python modules on real project tasks.

Exploring the Python Language and the Interpreter

Python is a dynamic but strictly typed programming language. It is both interpreted and compiled in that the original source code is compiled into byte code and then interpreted, but this happens transparently to the user; you do not have to explicitly ask Python to compile your code.

The Python language has several implementations, but the most common is the version written in C, often referred to as CPython. Other implementations include Jython, written in Java, and IronPython, written for the Microsoft .NET platform. CPython is the implementation used in this book.

NOTE At the time of writing, there are two version streams of Python: versions 2.x and 3.x. This book focuses on version 3, and the code has been tested on several releases within that stream—up to release 3.4. Where major compatibility issues arise with 2.x, reference will be made to version 2.7.

Python programs are written in text files that customarily have the extension .py. The Python interpreter, called python (in lowercase) does not actually care about the extension; it is only for the user’s benefit (and in some operating systems to allow the file and interpreter to be linked).

You can also input Python code directly to the interpreter. This method makes for a highly interactive development style where ideas are prototyped or tested in the interpreter and then transferred into a code editor. The Python interpreter is a powerful learning tool when you are starting to use a new concept or code module.

When working in this mode, you start the interpreter by typing python at an operating system command prompt. The system will respond with a message telling you the Python version and some build details, followed by the interactive prompt at which you type code. It looks like this:

  ActivePython 3.3.2.0 (ActiveState Software Inc.) based on   Python 3.3.2 (default, Sep 16 2013, 23:10:06) [MSC v.1600 32 bit (Intel)] on win   32   Type "help", "copyright", "credits" or "license" for more information.   >>>