```
def sumOfLeftLeaves(self, root):
"""
:type root: TreeNode
:rtype: int
"""
if root is None:
return 0
if root.left is None and root.right is None:#IF THE TREE HAS ONLY ONE NODE
return 0
return self.sumup(root)
def sumup(self,root):
if root is None:
return 0
if root.left is None and root.right is None:
return root.val
sum_left=self.sumup(root.left)
if root.right!=None and root.right.left is None and root.right.right is None:#JUST AS YOU CALCULATE SUM OF LEAF NODE JUST CHECK IF IT IS A RIGHT LEAF NODE SIMPLY SET SUM_RIGHT TO ZERO ELSE GO IN SIMILAR FASHION
sum_right=0
else:
sum_right=self.sumup(root.right)# GO IN SIMILAR FASHION
#print sum_left+sum_right
return sum_left+sum_right# RETURN THE CALCULATED VALUE FROM LEFT SUBTREE AND RIGHT SUBTREE
```