用python中序遍历二叉搜索树 并输出，然后将其转换为循环的双链表并输出，最后按正反序输出双链表中的所有元素

好的，我来给您讲解一下。

首先，我们需要定义一个二叉树节点类，包括节点值、左右子节点和指向父节点的指针。

class TreeNode:
    def __init__(self, val):
        self.val = val
        self.left = None
        self.right = None
        self.parent = None

接下来，我们可以先构建一棵二叉搜索树，并对其进行中序遍历，将遍历结果存储在一个列表中。

def inorder_traversal(root, res):
    if not root:
        return
    inorder_traversal(root.left, res)
    res.append(root.val)
    inorder_traversal(root.right, res)

root = TreeNode(4)
root.left = TreeNode(2)
root.left.left = TreeNode(1)
root.left.right = TreeNode(3)
root.right = TreeNode(5)

res = []
inorder_traversal(root, res)
print(res)  # [1, 2, 3, 4, 5]

接下来，我们需要将这棵二叉搜索树转化为循环的双链表。具体做法是，对于每个节点，将其左子节点的最右侧节点指向节点本身，将其右子节点的最左侧节点指向节点本身。

def convert_to_doubly_linked_list(root):
    if not root:
        return None
    convert_to_doubly_linked_list(root.left)
    if root.left:
        left_rightmost = root.left
        while left_rightmost.right:
            left_rightmost = left_rightmost.right
        left_rightmost.right = root
        root.left = left_rightmost
    if root.right:
        right_leftmost = root.right
        while right_leftmost.left:
            right_leftmost = right_leftmost.left
        right_leftmost.left = root
        root.right = right_leftmost
    convert_to_doubly_linked_list(root.right)
    return root

head = convert_to_doubly_linked_list(root)
while head.left:
    head = head.left
while head:
    print(head.val)
    head = head.right

最后，我们需要按照正反序输出双链表中的所有元素。具体做法是，分别从头和尾开始遍历双链表，输出节点值。

def print_doubly_linked_list(head):
    while head:
        print(head.val)
        head = head.right

print_doubly_linked_list(root)  # 正序
while root.right:
    root = root.right
print_doubly_linked_list(root)  # 反序

完整代码如下：

class TreeNode:
    def __init__(self, val):
        self.val = val
        self.left = None
        self.right = None
        self.parent = None

def inorder_traversal(root, res):
    if not root:
        return
    inorder_traversal(root.left, res)
    res.append(root.val)
    inorder_traversal(root.right, res)

root = TreeNode(4)
root.left = TreeNode(2)
root.left.left = TreeNode(1)
root.left.right = TreeNode(3)
root.right = TreeNode(5)

res = []
inorder_traversal(root, res)
print(res)  # [1, 2, 3, 4, 5]

def convert_to_doubly_linked_list(root):
    if not root:
        return None
    convert_to_doubly_linked_list(root.left)
    if root.left:
        left_rightmost = root.left
        while left_rightmost.right:
            left_rightmost = left_rightmost.right
        left_rightmost.right = root
        root.left = left_rightmost
    if root.right:
        right_leftmost = root.right
        while right_leftmost.left:
            right_leftmost = right_leftmost.left
        right_leftmost.left = root
        root.right = right_leftmost
    convert_to_doubly_linked_list(root.right)
    return root

head = convert_to_doubly_linked_list(root)
while head.left:
    head = head.left
while head:
    print(head.val)
    head = head.right

def print_doubly_linked_list(head):
    while head:
        print(head.val)
        head = head.right

print_doubly_linked_list(root)  # 正序
while root.right:
    root = root.right
print_doubly_linked_list(root)  # 反序