Tree

tree.py

class BinaryTree:
    def __init__(self, key, left=None, right=None):
        self.key = key
        self.left = left
        self.right = right

    def insert_left(self, key):
        if self.left:
            node = BinaryTree(key)
            node.left = self.left
            self.left = node
        else:
            self.left = BinaryTree(key)
    
    def insert_right(self, key):
        if self.right:
            node = BinaryTree(key)
            node.right = self.right
            self.right = node
        else:
            self.right = BinaryTree(key)

tree = BinaryTree("Les")
tree.insert_left("Cathy")
tree.insert_right("Sam")
tree.left.insert_left("Alex")
tree.left.insert_right("Frank")
tree.right.insert_left("Nancy")
tree.right.insert_right("Violet")

def preorder(tree):
    if not tree:
        return
    print(tree.key)
    preorder(tree.left)
    preorder(tree.right)
    
def inorder(tree):
    if not tree:
        return
    inorder(tree.left)
    print(tree.key)
    inorder(tree.right)

def postorder(tree):
    if not tree:
        return
    postorder(tree.left)
    postorder(tree.right)
    print(tree.key)

print("Pre-Order Traversal")
preorder(tree)
print("\nIn-Order Traversal")
inorder(tree)
print("\nPost-Order Traversal")
postorder(tree)