A Beginner's Guide to Using pyGTK and Glade

The beauty of pyGTK and Glade is they have opened up cross-platform, professional-quality GUI development to those of us who'd rather be doing other things but who still need a GUI on top of it all. Not only does pyGTK allow neophytes to create great GUIs, it also allows professionals to create flexible, dynamic and powerful user interfaces faster than ever before. If you've ever wanted to create a quick user interface that looks good without a lot of work, and you don't have any GUI experience, read on.

This article is the direct result of a learning process that occurred while programming Immunity CANVAS (www.immunitysec.com/CANVAS). Much of what was learned while developing the GUI from scratch was put in the pyGTK FAQ, located at www.async.com.br/faq/pygtk/index.py?req=index. Another URL you no doubt will be using a lot if you delve deeply into pyGTK is the documentation at www.gnome.org/~james/pygtk-docs. It is fair to say that for a small company, using pyGTK over other GUI development environments, such as native C, is a competitive advantage. Hopefully, after reading this article, everyone should be able to put together a GUI using Python, the easiest of all languages to learn.

As a metric, the CANVAS GUI was written from scratch, in about two weeks, with no prior knowledge of pyGTK. It then was ported from GTK v1 to GTK v2 (more on that later) in a day, and it is now deployed to both Microsoft Windows and Linux customers.

In a perfect world, you never would have to develop for anything but Linux running your favorite distribution. In the real world, you need to support several versions of Linux, Windows, UNIX or whatever else your customers need. Choosing a GUI toolkit depends on what is well supported on your customers' platforms. Nowadays, choosing Python as your development tool in any new endeavor is second nature if speed of development is more of a requirement than runtime speed. This combination leads you to choose from the following alternatives for Python GUI development: wxPython, Tkinter, pyGTK and Python/Qt.

Keeping in mind that I am not a professional GUI developer, here are my feelings on why one should chose pyGTK. wxPython has come a long way and offers attractive interfaces but is hard to use and get working, especially for a beginner. Not to mention, it requires both Linux and Windows users to download and install a large binary package. Qt, although free for Linux, requires a license to be distributed for Windows. This probably is prohibitive for many small companies who want to distribute on multiple platforms.

Tkinter is the first Python GUI development kit and is available with almost every Python distribution. It looks ugly, though, and requires you to embed Tk into your Python applications, which feels like going backward. For a beginner, you really want to split the GUI from the application as much as possible. That way, when you edit the GUI, you don't have to change a bunch of things in your application or integrate any changes into your application.

For these reasons alone, pyGTK might be your choice. It neatly splits the application from the GUI. Using libglade, the GUI itself is held as an XML file that you can continue to edit, save multiple versions of or whatever else you want, as it is not integrated with your application code. Furthermore, using Glade as a GUI builder allows you to create application interfaces quickly—so quickly that if multiple customers want multiple GUIs you could support them all easily.

Two main flavors of GTK are available in the wild, GTK versions 1 and 2. Therefore, at the start of a GUI-building project, you have to make some choices about what to develop and maintain. It is likely that Glade v1 came installed on your machine. You may have to download Glade v2 or install the development packages for GTK to compile the GTK v2 libglade. Believe me, it is worth the effort. GTK v2 offers several advantages, including a nicer overall look, installers for Windows with Python 2.2 and accessibility extensions that allow applications to be customized for blind users. In addition, version 2 comes installed on many of the latest distributions, although you still may need to install development RPMs or the latest pyGTK package.

GTK v2 and hence pyGTK v2 offer a few, slightly more complex widgets (Views). In the hands of a mighty GUI master, they result in awesome applications, but they really confuse beginners. However, a few code recipes mean you can treat them as you would their counterparts in GTK v1, once you learn how to use them.

As an example, after developing the entire GUI for CANVAS in GTK v1, I had to go back and redevelop it (which took exactly one day) in GTK v2. Support was lacking for GTK v1 in my customers' Linux boxes, but installing GTK v2 was easy enough. The main exception is Ximian Desktop, which makes pyGTK and GTK v1 easy to install. So, if your entire customer base is running that, you may want to stay with GTK v1. One thing to keep in mind though—a Python script is available for converting projects from Glade v1 to Glade v2, but not vice versa. So if you're going to do both, develop it first in Glade v1, convert it and then reconcile any differences.