Introduction to GUI Programming

Python codes can quickly be altered and re-run, a property that encourages direct editing of the source code to change parameters and program behavior. This type of hardcoded changes is usually limited to the developer of the code. However, the edit-and-run strategy may soon be error-prone and introduce bugs. Most users, and even the developer, of a script will benefit from some kind of user interface. In Chapter 2 we have defined user interfaces through command-line options, which are very convenient if a script is to be called from other scripts. A stand-alone application, at least as seen from an end-user, is often simpler to apply if it is equipped with a self-explanatory graphical user interface (GUI). This chapter explains how easy it is to add a small-size GUI to Python scripts.

To construct a GUI, one needs to call up functionality in a GUI toolkit. There are many GUI toolkits available for Python programmers. The simplest one is Tkinter [10], while PyGtk, PyQt [32,35], and wxPython [31] constitute more sophisticated toolkits that are gaining increased popularity. All of these toolkits require underlying C or C++ libraries to be installed on your computer: Tkinter, PyGtk, PyQt, and wxPython require the Tk, Gtk, Qt, and wxWindows libraries, respectively. Most Python installations have Tk incorporated, a fact that makes Tkinter the default GUI toolkit. Unless you are experienced with GUI programming, I recommend to start with Tkinter, since it is easier to use than PyGtk, PyQt, and wxPython. As soon as you find yourself working a significant amount of time with GUI development in Python, it is time to reconsider the choice of toolkit and your working style.