Thank you for the very interesting Tkinter Tricks (http://online.effbot.org/#20051113 posted on November 13). I just wanted to alert you to a simple error in the program as shown on the blog:

The first example defines a class MyController, but the code later on refers to it as ClickController.

As well, when I run the second example I encounter an error, but have not tracked it down. The refactored code presented as an alternative runs without error.

Thanks for your good work,
Alfred Milgrom (fredm [at] smartypantsco [dot] com)