[Tutor] Using dictionaries to call functions (Thanks)

[Kevin McCormick]

The explanations given were very helpful.  I have been trying to learn
some GUI stuff with Tkinter and the Grayson book.  He gives lots of
great example programs, but I'm not getting a good idea of how to use
classes and function calls from menu items.  He had a "dispatch table"
in one of the examples and now it is clear.

Anyone who wants to explain how the Grayson example "AppShell.py" (page
155) is used would be appreciated.  Later in the book, he uses it with
classes that are subclasses of AppShell, like Draw.py on page 238. 
Here, the Draw class is "class Draw(AppShell.AppShell):"  However, how
does one build from the top down, i.e. instead of the widget calling the
AppShell, how does the AppShell call the widget?