| 1 | import weakref |
| 2 | |
| 3 | class Node: |
| 4 | def __init__(self, value): |
| 5 | self.value = value |
| 6 | self._parent = None |
| 7 | self.children = [] |
| 8 | |
| 9 | def __repr__(self): |
| 10 | return 'Node({!r:})'.format(self.value) |
| 11 | |
| 12 | # property that manages the parent as a weak-reference |
| 13 | @property |
| 14 | def parent(self): |
| 15 | return self._parent if self._parent is None else self._parent() |
| 16 | |
| 17 | @parent.setter |
| 18 | def parent(self, node): |
| 19 | self._parent = weakref.ref(node) |
| 20 | |
| 21 | def add_child(self, child): |
| 22 | self.children.append(child) |
| 23 | child.parent = self |
| 24 | |
| 25 | if __name__ == '__main__': |
| 26 | root = Node('parent') |