Merge pull request #515 from KelvinG-611/master

Update 二叉树理论基础.md

problems/二叉树理论基础.md

@@ -206,7 +206,13 @@ public class TreeNode {
 
 
 Python：
-
+```python
+class TreeNode: 
+    def __init__(self, value):
+        self.value = value
+        self.left = None
+        self.right = None
+```
 
 Go：
 ```