Serialize and Deserialize Binary Tree

1class Codec:
2
3    def serialize(self, root):
4        """Encodes a tree to a single string.
5        
6        :type root: TreeNode
7        :rtype: str
8        """
9        if root is None:
10            return ""
11        
12        result = [str(root.val)]
13        nodes = collections.deque([root])
14
15        while len(nodes) > 0:
16            node = nodes.popleft()
17            
18            if node.left:
19                nodes.append(node.left)
20                result.append(str(node.left.val))
21            else:
22                result.append("null")
23            
24            if node.right:
25                nodes.append(node.right)
26                result.append(str(node.right.val))
27            else:
28                result.append("null")
29        
30        return ",".join(result)
31
32    def deserialize(self, data):
33        """Decodes your encoded data to tree.
34        
35        :type data: str
36        :rtype: TreeNode
37        """
38        if len(data) == 0:
39            return None
40        nodes = data.split(",")
41    
42        root = TreeNode(nodes[0])
43        assignments = collections.deque([root])
44        i = 1
45        while len(assignments) > 0:
46            node = assignments.popleft()
47            if i < len(nodes) and nodes[i] != "null":
48                node.left = TreeNode(nodes[i])
49                assignments.append(node.left)
50            i += 1
51            if i < len(nodes) and nodes[i] != "null":
52                node.right = TreeNode(nodes[i])
53                assignments.append(node.right)
54            i += 1
55        return root
56            
57