EP 26 Use Multiple Inheritance Only for Mix-in Utility Classes ref: http://qiita.com/giwa/items/a3a92b56049b84b9965a

file0.txt

import time

class ToDictMixin:
    def to_dict(self):
        return self._traverse_dict(self.__dict__)

    def _traverse_dict(self, instance_dict):
        output = {}
        for key, value in instance_dict.items():
            output[key] = self._traverse(key, value)
        return output

    def _traverse(self, key, value):
        time.sleep(0.2)
        if isinstance(value, ToDictMixin):
            print('ToDictMixin')
            return value.to_dict()
        elif isinstance(value, dict):
            print('dict')
            return self._traverse_dict(value)
        elif isinstance(value, list):
            print('list')
            return [self._traverse(key, i) for i in value]
        elif hasattr(value, '__dict__'):
            print('hasattr __dict__')
            return self._traverse_dict(value.__dict__)
        else:
            return value

class BinaryTree(ToDictMixin):
    def __init__(self, value, left=None, right=None):
        self.value = value
        self.left = left
        self.right = right

tree = BinaryTree(10, left=BinaryTree(7, right=BinaryTree(9)),
        right=BinaryTree(13, left=BinaryTree(11)))

# print(tree.to_dict())

file1.txt

class BinaryTreeWithParent(BinaryTree):
    def __init__(self, value, left=None, right=None, parent=None):
        super().__init__(value, left=left, right=right)
        self.parent = parent

    def _traverse(self, key, value):
        if (isinstance(value, BinaryTreeWithParent) and key == 'parent'):
            return value.value
        else:
            return super()._traverse(key, value)

root = BinaryTreeWithParent(10)
root.left = BinaryTreeWithParent(7, parent=root)
root.left.right = BinaryTreeWithParent(9, parent=root.left)
print(root.to_dict())

file2.txt

class NamedSubTree(ToDictMixin):
    def __init__(self, name, tree_with_parent):
        self.name = name
        self.tree_with_parent = tree_with_parent

my_tree = NamedSubTree('foobar', root)
print(my_tree.to_dict())