question about tree in python

[nospam]

How should I write a tree using diconary. I have used a dictonary to 
make a tree.

tree={best:collections.defaultdict(lambda:default)} in a id3 tree.

Is there a way to multple values and when then only return on type of 
values.

I tried this apporach but it did not work.

class Tree:
     def __init__(self):
         pass



     def ini(self,default_tree,d_attr):
         self.tree={d_attr:collections.defaultdict(lambda:default_tree)}
         self.tree_A={d_attr:collections.defaultdict(lambda:default_tree)}
         self.tree_I={d_attr:collections.defaultdict(lambda:default_tree)}
         self.tree_p={d_attr:collections.defaultdict(lambda:default_tree)}
         self.tree_n={d_attr:collections.defaultdict(lambda:default_tree)}
         return self.tree

     def __call__(self,best,val,subtree):
         self.tree[best][val]=subtree

     def 
input_tree(self,best,val,subtree,postive,negative,attribute_value,info_gain):
         tree=self.tree
         print best
         print val
         tree[best][val]=subtree
         print self.tree
         self.tree_A[best][val]= attribute_value
         self.tree_I[best][val]= info_gain
         self.tree_p[best][val]= postive
         self.tree_n=negative
         tree=self.tree
         return tree