It is very useful during XML program development to be able to see the tree structure of an XML file. The C3 is a Python utility that is part of the Pyxie Open Source Project that does exactly that. It is implemented with the wxPython cross-platform GUI toolkit, which we will use extensively in this book.
The wxPython toolkit is a wrapping of the cross-platform GUI toolkit for C++ programmers, which is called wxWindows. The wxPython toolkit is the work of Robin Dunne (http://alldunn.com/wxPython). The wxWindows toolkit is the work of Julian Smart (http://www.wxwindows.org). Before executing the C3 application, we will need to get wxPython up and running on your machine.