The Structure of the Book

The book is divided into four parts. Part I is primarily a rapid conversion course aimed at non-Python programmers who are familiar with an object-oriented language, although it also has some (clearly marked) PyQt content. Because the core Python language is mostly simple and is quite small, these chapters can teach the basics of Python to a sufficient extent that real Python applications can be written.

If you think that you can pick up the Python syntax simply through reading it, you might be tempted to skip Part I and dive straight into the GUI programming that begins in Part II. The early chapters in Part II include back-references to the relevant pages in Part I to support readers who choose this approach. However, even for readers familiar with Python, we recommend reading about QString in Chapter 1. If you are unfamiliar with partial function application (currying), it is important to read the subsection that covers this in Chapter 2, since this technique is sometimes used in GUI programming.

★There are also Python bindings for the older Qt 3 library, but there is no reason to use that library for new projects, especially since Qt 4 offers far more functionality and is easier to use.

Part II begins by showing three tiny PyQt GUI applications to give an initial impression of what PyQt programming is like. It also explains some of the fundamental concepts involved in GUI programming, including PyQt's highlevel signals and slots communication mechanism. Chapter 5 shows how to create dialogs and how to create and lay out widgets ("controls" in Windows-speak—the graphical elements that make up a user interface such as buttons, listboxes, and such) in a dialog. Dialogs are central to GUI programming: Most GUI applications have a single main window, and dozens or scores of dialogs, so this topic is covered in depth.

After the dialogs chapter comes Chapter 6, which covers main windows, including menus, toolbars, dock windows, and keyboard shortcuts, as well as loading and saving application settings. Part II's final chapters show how to create dialogs using Qt Designer, Qt's visual design tool, and how to save data in binary, text, and XML formats.

Part III gives deeper coverage of some of the topics covered in Part II, and introduces many new topics. Chapter 9 shows how to lay out widgets in quite sophisticated ways, and how to handle multiple documents. Chapter 10 covers low-level event handlers, and how to use the clipboard as well as drag and drop, text, HTML, and binary data. Chapter 11 shows how to modify and subclass existing widgets, and how to create entirely new widgets from scratch, with complete control over their appearance and behavior. This chapter also shows how to do basic graphics. Chapter 12 shows how to use Qt 4.2's new graphics view architecture, which is particularly suited to handling large numbers of independent graphical objects. Qt's HTML-capable rich text engine is covered in Chapter 13. This chapter also covers printing both to paper and to PDF files.

Part III concludes with two chapters on model/view programming: Chapter 14 introduces the subject and shows how to use Qt's built-in views and how to create custom data models and custom delegates, and Chapter 15 shows how to use the model/view architecture to perform database programming.

Part IV continues the model/view theme, with coverage of three different advanced model/view topics in Chapter 16. The first section of Chapter 17 describes the techniques that can be used for providing online help, and the second section explains how to internationalize an application, including how to use Qt's translation tools to create translation files. The Python standard library provides its own classes for networking and for threading, but in the last two chapters of Part IV we show how to do networking and threading using PyQt's classes.

Appendix A explains where Python, PyQt, and Qt can be obtained, and how to install them on Windows, Mac OS X, and Linux. PyQt is much easier to learn if you install it and try out some of the exercises, and if you inspect some of the example code. Appendix B presents screenshots and brief descriptions of selected PyQt widgets; this is helpful for those new to GUI programming. Appendix C presents diagrams of some of PyQt's key class hierarchies; this is useful for getting to know what classes PyQt has to offer and how they are related.

If you have never used Python before, you should begin by reading Chapters 1-6 in order. If you already know Python, at least read the string policy (in bullet points on page 28), and skim the material in Chapter 2 (apart from the first section, which you'll know well). Make sure that you are comfortable with lambda and partial function application, both of which are covered in Chapter 2. It is probably also worth skimming Chapter 3 as well. Then read Chapters 4, 5, and 6 in order.

Once you have covered the first six chapters, you have covered the essentials of Python and the fundamentals of PyQt.

Chapter 7 is useful if you want to know how to create dialogs using a visual design tool rather than purely by hand coding, something that can save a lot of time. For file handling, at least read the first three sections of Chapter 8. If you plan to write and read text files, also read Chapter 8's fourth section, and similarly the fifth section if you are going to use XML files.

For Part III, at the least read Chapter 10's first section, on event handling, and all of Chapter 11. Chapter 12 and the first section of Chapter 13 assume that you have read about PyQt's event handling, and that you have read Chapter 11. Chapters 9 and 14 can be read stand-alone in this part, but Chapter 15 assumes that you have read Chapter 14.

In Part IV, Chapter 16 assumes that you have read Chapters 14 and 15, but the other chapters can be read independently.

If you find errors in the text or in the examples, or have other comments, please write to [email protected] quoting "PyQt book" in the subject line. The book's home page, where any corrections will be published, and from where the examples and exercise solutions can be downloaded, is http://www.qtrac.eu/ pyqtbook.html.

If you want to participate in the PyQt community, it is worthwhile joining the mailing list. Goto http://www.riverbankcomputing.com/mailman/listinfo/pyqt to find a link to the archive, so that you can see what the mailing list is like, and also for a form for joining. Python also has mailing lists and other community activities. For these, go to http://www.python.org/community.

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