simple bidirectional tree

node.py

class NodeList(list):
    def __init__(self, root, items):
        self.root = root
        super(NodeList, self).__init__(items)

    def append(self, item):
        item._parent = self.root
        super(NodeList, self).append(item)

class Node(object):
    def __init__(self, name, parent=None, children=None):
        self.name = name
        self.children = children 
        self._parent = None
        self.parent = parent

    @property
    def parent(self):
        return self._parent

    @parent.setter
    def parent(self, value):
        if value == self._parent:
            return

        if self._parent:
            if self._parent.children:
                self._parent.children.remove(self)

        if value:
            if value.children:
                value.children.append(self)
            else:
                value.children = NodeList(value, [self])

        self._parent = value

    def __repr__(self):
        return 'N:{}'.format(self.name)


if __name__ == '__main__':
    root = Node('root')
    omar = Node('omar', parent=root)
    joe = Node('joe', parent=root)

    assert root.name == 'root'
    assert len(root.children) == 2

    other = Node('other')
    omar.parent = other

    assert other.name == 'other'
    assert len(other.children) == 1
    assert len(root.children) == 1

    last = Node('last')
    other.children.append(last)

    assert len(other.children) == 2
    assert last.parent == other