Question

Basically I want to be able to have each node of type tree have a Data field and a list of branches. This list should contain a number of objects of type Tree.
I think I have the actual implementation of the list down, but I get strange behavior when I try using the getLeaves method. Basically it calls itself recursively and never returns, and the way that happens is somehow the second node of the tree gets it’s first branch set as itself (I think).

class Tree:
    """Basic tree graph datatype"""
    branches = []

    def __init__(self, root):
        self.root = root

    def addBranch (self, addition):
    """Adds another object of type Tree as a branch"""
        self.branches += [addition]

    def getLeaves (self):
        """returns the leaves of a given branch. For leaves of the tree, specify root"""
        print (len(self.branches))
        if (len(self.branches) == 0):
            return self.root
        else:
            branchSum = []
            for b in self.branches:
                branchSum += b.getLeaves()
            return (branchSum)

Answer 1

Your ‘branches’ variable is a class member, not an instance member. You need to initialize the ‘branches’ instance variable in the constructor:

class Tree:
    """Basic tree graph datatype"""

    def __init__(self, root):
       self.branches = []
       self.root = root

The rest of your code looks good.