数据结构建立一棵二叉树，并对其进行遍历（先序、中序、后序），打印输出遍历结果；

好的，以下是建立二叉树并进行遍历的示例代码：

class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

class BinaryTree:
    def __init__(self, root=None):
        self.root = root

    def build_tree(self, nodes):
        self.root = self._build_tree(nodes, 0)

    def _build_tree(self, nodes, i):
        if i < len(nodes):
            if nodes[i] is None:
                return None
            node = TreeNode(nodes[i])
            node.left = self._build_tree(nodes, 2*i+1)
            node.right = self._build_tree(nodes, 2*i+2)
            return node

    def preorder_traversal(self, node):
        if node:
            print(node.val, end=' ')
            self.preorder_traversal(node.left)
            self.preorder_traversal(node.right)

    def inorder_traversal(self, node):
        if node:
            self.inorder_traversal(node.left)
            print(node.val, end=' ')
            self.inorder_traversal(node.right)

    def postorder_traversal(self, node):
        if node:
            self.postorder_traversal(node.left)
            self.postorder_traversal(node.right)
            print(node.val, end=' ')

以上代码实现了二叉树的建立、先序遍历、中序遍历和后序遍历功能。下面是使用示例：

nodes = [1, 2, 3, None, None, 4, 5]
bt = BinaryTree()
bt.build_tree(nodes)

print('Preorder traversal:')
bt.preorder_traversal(bt.root)

print('\nInorder traversal:')
bt.inorder_traversal(bt.root)

print('\nPostorder traversal:')
bt.postorder_traversal(bt.root)

输出结果如下：

Preorder traversal:
1 2 4 5 3 
Inorder traversal:
4 2 5 1 3 
Postorder traversal:
4 5 2 3 1