class TreeNode:

  def __init__(self, data):

    self.data = data

    self.left = None

    self.right = None

​

def preOrderTraversal(node):

  if node is None:

    return

  print(node.data, end=", ")

  preOrderTraversal(node.left)

  preOrderTraversal(node.right)

​

root = TreeNode('R')

nodeA = TreeNode('A')

nodeB = TreeNode('B')

nodeC = TreeNode('C')

nodeD = TreeNode('D')

nodeE = TreeNode('E')

nodeF = TreeNode('F')

nodeG = TreeNode('G')

​

root.left = nodeA

root.right = nodeB

​

nodeA.left = nodeC

nodeA.right = nodeD

​

nodeB.left = nodeE

nodeB.right = nodeF

​

nodeF.left = nodeG

​

# Traverse

preOrderTraversal(root)

​