generate tree graph by pydot

basics

http://pythonhaven.wordpress.com/2009/12/09/generating_graphs_with_pydot/

you may need recursive one

http://stackoverflow.com/questions/13688410/dictionary-object-to-decision-tree-in-pydot
http://stackoverflow.com/questions/5575124/python-combine-several-nested-lists-into-a-dictionary

you can even make graphical models as you like!!

http://jseabold.net/blog/2012/02/12/making-graphical-models-with-pydot/