[Tutor] Help with objects

[bob]

At 09:04 PM 11/21/2005, Vincent Wan wrote:
>Thank you bob. I fixed the errors where I tried to index a dictionary
>with name()
>so so that they say name[]
>
>>>Beyond the error I'm still not sure I understand how to make and
>>>use a tree data structure using objects.
>
>There is a new error as well
>
>Traceback (most recent call last):
>   File "/Users/Wally/obj_tree1.py", line 28, in -toplevel-
>     currentTree = Tree()
>   File "/Users/Wally/obj_tree1.py", line 21, in __init__
>     nodeList[0] = Tree.Node(0)    # adds a root node 0 to the tree
>NameError: global name 'nodeList' is not defined
>
>Code with error bob fixed fixed throughout
>
># obj_tree1.py
>
>import random
>
># constants that control the simulation
>NUMBER_REPS = 10        # run's the simulation
>MAX_LINAGES = 10        # number of species in each run
>BRANCHING_PROBABILITY = 0.5
>
>class Tree(object):
>     numLinages = 0    # keeps track of how many nodes there are
>     nodeList = {}    # keeps track of the nodes

nodeList is a property of class Tree.

>     class Node(object):
>         def __init__(self, name):
>             self.name = name    # an integer
>             self.alive = True
>             self.descendents = {}    # nodes descending from self
>             Tree.numLinages += 1    # records node creation
>             Tree.nodeList[self.name] = self    # makes node 
> accesable from tree
>     def __init__(self):
>         nodeList[0] = Tree.Node(0)    # adds a root node 0 to the tree

To refer to a property of the class: Tree.nodeList[0] = 
Tree.Node(0)    # adds a root node 0 to the tree

>     def AddBranch(self, offspring):
>         self.descendents[offspring] = Tree.Node(offspring)    # 
> adds a descendent node
>     def NumLinages( ):
>         return Tree.numLinages
>     NumLinages = staticmethod(NumLinages)
>
>currentTree = Tree()
>
>for i in range(NUMBER_REPS):
>     j = 0
>     while j <= currentTree.NumLinages():   # checks all node because
>their names are sequential integers
>         if j.alive:
>             if random.random() >= BRANCHING_PROBABILITY:
>                 currentTree.AddBranch(j, (currentTree.NumLinages() +
>1)) # creates a new node
>         j += 1
>
>Thank you for the help
>
>
>Vincent Wan
>
>------------------------------------------------------------------------ 
>--------------
>PhD Candidate
>Committee on the Conceptual and Historical Studies of Science
>University of Chicago
>
>PO Box 73727
>Fairbanks, AK 99707
>
>wan AT walrus DOT us (change CAPS to @ and . )