為什么不打印樹？

Question

我正在嘗試創建一個Tree類，我首先創建一個樹節點類，然后開始制作樹模塊。 我嘗試創建的第一種方法是print_tree 。

我遍歷樹的策略是：

1. 去找孩子
2. 如果節點沒有子節點，則轉到兄弟節點，否則，轉到父節點的兄弟節點
3. 如果父節點為None則中斷（這意味着我們回到了根節點）

但它不起作用。 為什么？

class treeNode:
    def __init__(self,data):
        self.data = data
        self.children = []
        self.parent = None
        self.nextSibling = None
        self.level = 0

        def add_children(self,*child):
            for i in child:
                i.parent = self
                self.children.append(i)
                self.children[-1].nextSibling = i.data

        def level_func(self):
            itr = self
            count = 0
            while itr:
                count += 1
                itr = itr.parent
            self.level = count - 1

class Tree:
    def __init__(self,root:treeNode):
        self.root = root

    def print_tree(self):
        print(self.root.data)
        kid = self.root.children[0]
        while (kid != self.root):
            kid.level_func()
            print(" " * (3 * kid.level),kid.data)
            if len(kid.children) == 0:
                while kid.nextSibling is None or kid.parent is None:
                    kid = kid.parent
                else:
                    kid = kid.nextSibling
            else:
                kid = kid.children[0]

parent = treeNode(1)
child = treeNode(2)
parent.add_children(child,treeNode(3),treeNode(4),treeNode(5))
grand = treeNode(6)
child.add_children(grand,treeNode(7))
tree1 = Tree(parent)
tree1.print_tree()

Answer 1

您應該讓節點通過遞歸處理遍歷。 要打印，請實現__repr__()方法，以便您可以直接在樹節點上使用 print()：

class treeNode:

    ...
    
    # list of lines to print for this node and its descendants 

    def lines(self,indent="",indent2=""): # node indent, children indent
        result = [indent+str(self.data)]       # line for node data
        for last,child in enumerate(self.children,1-len(self.children)):
            lines=child.lines(indent2+"|__ ",indent2+["|   ","    "][last==0]))
            result.extend(lines)               # add descendant lines
        return result

    def __repr__(self):
        return "\n".join(self.lines())

輸出：

parent = treeNode(1)
child = treeNode(2)
parent.add_children(child,treeNode(3),treeNode(4),treeNode(5))
grand = treeNode(6)
child.add_children(grand,treeNode(7))
parent.children[-1].add_children(treeNode(10))
tree1 = Tree(parent)

print(tree1.root)

1
|__ 2
|   |__ 6
|   |__ 7
|__ 3
|__ 4
|__ 5
    |__ 10

print(child)

2
|__ 6
|__ 7