Update 0404.左叶子之和.md

python version added

problems/0404.左叶子之和.md

@@ -205,8 +205,25 @@ class Solution {
 
 
 Python：
-
-
+```Python
+**递归**
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def sumOfLeftLeaves(self, root: TreeNode) -> int:
+        self.res=0
+        def areleftleaves(root):
+            if not root:return
+            if root.left and (not root.left.left) and (not root.left.right):self.res+=root.left.val
+            areleftleaves(root.left)
+            areleftleaves(root.right)
+        areleftleaves(root)
+        return self.res
+```
 Go：