python - 实现一个 child 和 parent 可以互相引用的树

Question

来自 http://cbio.ufs.ac.za/live_docs/nbn_tut/trees.html

Let's create a python class to represent a tree. We need some way to store data in a node, and some way to indicate any child nodes, or subtrees.

class node(object):
    def __init__(self, value, children = []):
        self.value = value
        self.children = children

Whoa! That seems way too easy... but believe it or not, it does the job. Let's use our new class to store our family tree...

tree = node("grandmother", [
    node("daughter", [
        node("granddaughter"),
        node("grandson")]),
    node("son", [
        node("granddaughter"),
        node("grandson")])
    ]);

我希望能够获得每个 node 实例的子节点和父节点，所以我认为我需要同时定义其父节点和子节点

class node(object):
    def __init__(self, value, children = [], parent = []):
        self.value = value
        self.children = children
        self.parent = parent

但问题是每个节点在其每个子节点和父节点中都会有一个副本。如果我更改它的值，我将不得不更改其副本中的所有值。在 C++ 中，没有这样的问题，因为我们可以通过将指向其子节点和父节点的指针仅存储在节点中来引用节点的子节点和父节点。我想知道如何在 Python 中实现这样的树？谢谢。

Answer 1

您可以在节点构造函数中分配 child 的 parent :

class node(object):
    def __init__(self, value, children = None):
        self.value = value
        self.children = children or []
        self.parent = None
        for child in self.children:
            child.parent = self