Chapter 17. Tkinter GUIs

Most professional client-side applications interact with the user through a graphical user interface (GUI). A GUI is programmed through a toolkit, which is a library that supplies controls (also known as widgets), visible objects such as buttons, labels, text entry fields, and menus. A GUI toolkit lets you compose controls into a coherent whole, display them on-screen, and interact with the user, receiving input via keyboard and mouse.

Python gives you a choice among many GUI toolkits. Some are platform-specific, but most are cross-platform, supporting at least Windows and Unix-like platforms and often the Mac as well. http://wiki.python.org/moin/GuiProgramming lists dozens of GUI toolkits for Python. The most popular Python GUI toolkit today is probably wxPython (http://www.wxpython.org/), but the one distributed with Python itself is Tkinter.

Tkinter is an object-oriented Python wrapper around the cross-platform toolkit Tk, which is also used with other scripting languages such as Tcl (for which it was originally developed), Ruby, and Perl. Tkinter, like the underlying Tcl/Tk, runs on Windows, Macintosh, and Unix-like platforms. On Windows, the standard Python distribution also includes, as well as Tkinter itself, the Tcl/Tk library needed to run Tkinter. On other platforms, you may have to obtain and install Tcl/Tk separately (you may also have to install or reinstall Python after Tcl/Tk, depending on the Python distribution's details).

This chapter covers an essential subset of Tkinter that is sufficient to build simple graphical frontends for Python applications. (More complete documentation is available at http://docs.python.org/lib/tkinter.html.) All the scripts in this chapter are meant to be run standalone (i.e., from a command line, or in a platform-dependent way, such as by double-clicking on a script's icon). Running a GUI script from inside another program that has its own GUI, such as a Python integrated development environment (e.g., IDLE or PythonWin), can often cause anomalies. This can be a particular problem when the GUI script attempts to terminate (and thus close down the GUI), since the script's GUI and the development environment's GUI may interfere with each other.