Python Code To Print A Binary Tree

A binary tree is a type of data structure in which each node has at most two children, referred to as the left child and the right child. Binary trees are used in various aspects of computer science including sorting and searching. In this tutorial, we will create a binary tree in Python and complete Python code to print a binary tree.

Table of Contents

Step 1: Define the Binary Tree

Firstly, we need to create the binary tree structure. Here, we’ll define a simple Node class:

class Node:
    def __init__(self, data):
        self.data = data
        self.left = None
        self.right = None

This class represents a node in the binary tree, which contains some data and pointers to its left and right children.

Step 2: Insert Data Into the Binary Tree

To insert data into the tree, we’ll define an insert function:

def insert(root, data):
    if root is None:
        return Node(data)
    else:
        if data <= root.data:
            root.left = insert(root.left, data)
        else:
            root.right = insert(root.right, data)
        return root

In this function, if the tree is empty (i.e., the root is None), we create a new node with the given data and return it. If the tree is not empty, we recursively insert the data into the left or right subtree depending on its value.

Step 3: Print the Binary Tree

There are several ways you can “print” a binary tree. Here, we’ll implement in-order, pre-order, and post-order traversal methods:

In-Order Traversal: In this traversal method, the left subtree is visited first, then the root and later the right subtree.

def print_inorder(root):
    if root:
        print_inorder(root.left)
        print(root.data, end=" ")
        print_inorder(root.right)

Pre-Order Traversal: In this traversal method, the root node is visited first, then the left subtree and finally the right subtree.

def print_preorder(root):
    if root:
        print(root.data, end=" ")
        print_preorder(root.left)
        print_preorder(root.right)

Post-Order Traversal: In this traversal method, the root node is visited last. First, we traverse the left subtree, then the right subtree, and finally the root node.

Step 4: Python Code to Print a Binary Tree

Here is the complete code:

class Node:
    def __init__(self, data):
        self.data = data
        self.left = None
        self.right = None

def insert(root, data):
    if root is None:
        return Node(data)
    else:
        if data <= root.data:
            root.left = insert(root.left, data)
        else:
            root.right = insert(root.right, data)
        return root

def print_inorder(root):
    if root:
        print_inorder(root.left)
        print(root.data, end=" ")
        print_inorder(root.right)

def print_preorder(root):
    if root:
        print(root.data, end=" ")
        print_preorder(root.left)
        print_preorder(root.right)

def print_postorder(root):
    if root:
        print_postorder(root.left)
        print_postorder(root.right)
        print(root.data, end=" ")

root = Node(50)

root = insert(root, 30)
root = insert(root, 20)
root = insert(root, 40)
root = insert(root, 70)
root = insert(root, 60)
root = insert(root, 80)

print("In-order traversal:")
print_inorder(root)

print("\nPre-order traversal:")
print_preorder(root)

print("\nPost-order traversal:")
print_postorder(root)

When you run this code, it will create a binary tree and print the tree using in-order, pre-order, and post-order traversals.

Conclusion

In this Python tutorial, I explained binary tree in Python and Python Code to Print a Binary Tree.