[Tutor] subclassing across multiple modules

[Lloyd Kvam]

You want a method in a base class to parse input and create instances of
certain derived classes.  Your sample code looks like:
if some_condition_on_chunk_contents:
     node = Node1(chunk_contents)
else:
     node = Node2(chunk_contents)

I'd suggest changing the method to use a variable to determine the
class.  Following your pattern of coding:
#Toolkit.py
class Tree:
	node1 = Node1
	node2 = Node2
	...
class Node1(Node):
	...

#Application.py
class Tree(Toolkit.Tree):
	node1 = Node1
	node2 = Node2
	...
class Nodes(Node,Toolkit.Node1):
	...

if some_condition_on_chunk_contents:
     node = self.node1(chunk_contents)
else:
     node = self.node2(chunk_contents)

This requires that the class constructors be similar enough so that they
take the same parameters.  It is also a manual effort to keep the node
assignments in Tree in sync with the Node classes that you write.  You
also face a similar issue keeping Application.py and Toolkit.py in sync.

-- 
Lloyd Kvam
Venix Corp