Before we start wading into the Tkinter pond, let's begin with some perspective on Python GUI options in general. Because Python has proven to be such a good match for GUI work, this domain has seen much activity in recent years. In fact, although Tkinter is the most widely used GUI toolkit in Python, there is a variety of ways to program user interfaces in Python today. Some are specific to Windows or X Windows, some are cross-platform solutions, and all have followings and strong points all their own. To be fair to all the alternatives, here is a brief inventory of GUI toolkits available to Python programmers as I write these words:
 In this book, "Windows" refers to the Microsoft Windows interface common on PCs, and "X Windows" refers to the X11 interface most commonly found on Unix and Linux platforms. These two interfaces are generally tied to the Microsoft and Unix platforms, respectively. It's possible to run X Windows on top of a Microsoft operating system and Windows emulators on Unix and Linux, but not common.
Tkinter (shipped with Python)
An open-source, portable GUI library, used as the de facto standard for GUI development in Python. Tkinter makes it easy to build simple GUIs quickly, and can be straightforwardly augmented with larger component frameworks in Python. Python scripts that use Tkinter to build GUIs run portably on Windows, X Windows (Unix), and Macintosh, and display a native look-and-feel on each of these. The underlying Tk library used by Tkinter is a standard in the open source world at large, and is also used by the Perl and Tcl scripting languages.
An open-source Python interface for wxWindows -- a portable GUI class framework originally written to be used from the C++ programming language. The wxPython system is an extension module that wraps wxWindows classes. This library is generally considered to excel at building sophisticated interfaces, and is probably the second most popular Python GUI toolkit today, behind Tkinter. At this writing, wxPython code is portable to Windows and Unix-like platforms, but not the Macintosh. The underlying wxWindows library best supports Windows and GTK (on Unix), but it is generally portable to Windows, Unix-like platforms, and the Macintosh.
As we will see in Chapter 15, JPython (a.k.a. "Jython") is a Python port for Java, which gives Python scripts seamless access to Java class libraries on the local machine. Because of that, Java GUI libraries such as swing and awt become another way to construct GUIs in Python code run by the JPython system. Such solutions are obviously Java-specific, and limited in portability to the portability of Java and its libraries. A new package named jTkinter also provides a Tkinter port to JPython using Java's JNI; if installed, Python scripts may also use Tkinter to build GUIs under JPython.
KDE and Qt (http://www.thekompany.com/projects/pykde)
Gnome and GTK (ftp://ftp.daa.com.au/pub/james/python)
On Linux, developers can find Python interfaces to the underlying GUI libraries at the core of the KDE and Gnome window systems. The PyKDE and PyQt extension packages provide access to KDE development libraries (PyKDE requires PyQt). The gnome-python and PyGTK extension packages export Gnome and GTK toolkit calls for use in Python scripts (gnome-python requires PyGTK). Both of these sets of extensions are as portable as the underlying libraries they use. Today, the Qt class library runs on Unix and Windows, KDE runs on Linux and Unix platforms, and GTK and Gnome run on Linux and Unix platforms (though a Windows port of GTK is in the works). See relevant web sites for more recent details.
The Windows win32all.exe extensions package for Python, available at Python's web site and on this book's CD-ROM, includes wrappers for the Microsoft Foundation Classes (MFC) framework -- a development library that includes user interface components. With the Windows extensions, Python programs can construct Windows GUIs using the same MFC calls applied in languages such as Visual C++. Pythonwin, an MFC sample program that implements a Python development GUI, is included with the extensions package. This is a Windows-only solution, but may be an appealing option for developers with a prior intellectual investment in using the MFC framework from Visual C++.
An MFC-like GUI library for Python, ported to run on both X Windows for Unix (where it uses Tk) and Windows for PCs (where it uses MFC). WPY scripts run unchanged on each platform, but use MFC coding styles.
Interfaces to the raw X Windows and Motif libraries also exist for Python. They provide maximum control over the X11 development environment, but are an X-only solution.
There are other lesser-known GUI toolkits for Python, and new ones are likely to emerge by the time you read this book (e.g., the newly announced Python port to the .NET framework on Windows may offer user interface options as well). Moreover, package and web site names like those in this list mutate over time. For an up-to-date list of available tools, see http://www.python.org and the new "Vaults of Parnassus" third-party packages site currently at http://www.vex.net/parnassus.
 In Part III, we'll learn how to build user interfaces within a web browser. For now, we'll focus on more traditional GUIs that may or may not be connected to a network.