I am not used to generators and wonder how to make code cleaner/Pythonic? in the generator part.

The function is about validating a binary search tree. The inorder_gen function yield one element a time. The main function compares the value yielded and previous yielded value to determine whether BST’s invariant is violated.

# Definition for a binary tree node. # class TreeNode(object): #     def __init__(self, x): #         self.val = x #         self.left = None #         self.right = None  class Solution(object):      def isValidBST(self, root):         """         :type root: TreeNode         :rtype: bool         """         last_val = None         for idx, v in enumerate(self.inorder_gen(root)):             if idx != 0 and v <= last_val:                 return False             last_val = v         return True      def inorder_gen(self, node):         if node is None:             return          if node.left != None:             for v in self.inorder_gen(node.left):                 yield v         yield node.val         if node.right != None:             for v in self.inorder_gen(node.right):                 yield v 

Please let me know if I did not make it clear. I appreciate your help.