pre-order.py

class Node:
   def __init__(self, data):
      self.left = None
      self.right = None
      self.data = data
# Insert Node
   def insert(self, data):
      if self.data:
         if data < self.data:
            if self.left is None:
               self.left = Node(data)
            else:
               self.left.insert(data)
         else if data > self.data:
            if self.right is None:
               self.right = Node(data)
            else:

               self.right.insert(data)
      else:
         self.data = data
# Print the Tree
   def PrintTree(self):
      if self.left:
         self.left.PrintTree()
print( self.data),
if self.right:
self.right.PrintTree()
# Postorder traversal
# Left ->Right -> Root
def PostorderTraversal(self, root):
res = []
if root:
res = self.PostorderTraversal(root.left)
res = res + self.PostorderTraversal(root.right)
res.append(root.data)
return res
root = Node(27)
root.insert(14)
root.insert(35)
root.insert(10)
root.insert(19)
root.insert(31)
root.insert(42)
print(root.PostorderTraversal(root))