根据java 题解改写的python代码

# -*- coding:utf-8 -*-
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
class Solution:
    def Convert(self, pRootOfTree):
        # write code here
        if not pRootOfTree:
            return None
        if (pRootOfTree.left == None and pRootOfTree.right == None):
            return pRootOfTree
        # 1.将左子树构造成双链表，并且返回链表头节点
        left = self.Convert(pRootOfTree.left)
        p =left

        # 2.定位到左子树双链表最后一个节点
        while(p!=None and p.right!=None):
            p = p.right
        
        # 3.如果左子树构成的双向链表不为空的话，将当前的root追加到左子树链表
        if left != None:
            p.right = pRootOfTree
            pRootOfTree.left = p
        # 4.将右边子树构造成双链表，并返回链表头节点
        right = self.Convert(pRootOfTree.right)

        # 5.如果右子树链表不为空，将该链表追加到root节点之后

        if right != None:
            right.left = pRootOfTree
            pRootOfTree.right = right
        # 6.根据左子树链表是否为空确定返回的节点。
        while(pRootOfTree.left):
            pRootOfTree=pRootOfTree.left
        return pRootOfTree