What Is A Data Structure – Complete Guide

Welcome to an exciting journey into the world of data structures! Whether you’re just starting out with coding or you’re an experienced developer looking to sharpen your skills, understanding data structures is a foundational step in the world of programming. By the end of this tutorial, you’ll have a firmer grasp of how data structures work, why they’re so important, and how they can be applied in various programming scenarios. Let’s dive into the fundamental concepts and practical examples that will make data structures an integral part of your coding toolkit.

What Are Data Structures?

Data structures are one of the key ingredients in writing efficient and effective code. They are the mechanisms that enable storage, organization, and retrieval of data within a computer program. Think of data structures as different ways of arranging and storing data so that it can be accessed and worked with effectively. Imagine data structures like the assortment of organizational tools in a toolbox, each with a specific purpose and ideal for certain tasks.

What Are Data Structures Used For?

Data structures are used for handling, storing, and organizing data in a way that allows for operations to be performed on it effectively. They are crucial when it comes to designing algorithms and implementing software. From managing large datasets in database systems to controlling the flow of information in web applications, data structures make complex tasks manageable and efficient.

Why Should I Learn Data Structures?

Learning about data structures is a must for any aspiring programmer. Here’s why:

  • Performance: The right data structure can significantly speed up the execution of your code.
  • Maintainability: Well-chosen data structures can lead to cleaner, more maintainable code.
  • Problem-solving: Data structures are the tools that help you conquer complex coding challenges and algorithmic puzzles.
  • Employability: A solid grasp of data structures is often expected by employers and can set you apart from the competition.

Now that you understand what data structures are, what they’re for, and why they’re so vital to your development as a coder, it’s time to get our hands on some code and see how these concepts apply in practice!

CTA Small Image

Arrays and Lists

Let’s start by examining two of the simplest and most widely used data structures: arrays and lists. An array is a collection of elements, all of the same type, stored in contiguous memory locations. Lists, or arrays that grow and shrink dynamically, are more flexible than static arrays. Here are some basic operations:

// Declaration of an array in Java
int[] numbers = new int[5];

// Initializing an array in Python
numbers = [0] * 5

Arrays allow you to store elements and access them quickly using an index. Here’s an example of accessing and modifying an element in an array:

// Accessing the third element (index 2) in Java
int value = numbers[2];

// Modifying the third element in Python
numbers[2] = 10

While arrays are fixed in size, lists in many languages can change size dynamically. The ArrayList in Java, for example, allows for adding and removing elements:

// Creating an ArrayList in Java
ArrayList<Integer> dynamicNumbers = new ArrayList<>();

// Adding elements to the ArrayList

// Removing the first element (index 0)

Now, let’s look at iteration over these collections:

// Iterating over an array in Java
for (int i = 0; i < numbers.length; i++) {

// Iterating over a list in Python using a for loop
for number in numbers:

Stacks and Queues

Stacks and queues are data structures that differ mainly in how elements are removed. Stacks follow a last-in-first-out (LIFO) principle, while queues operate on a first-in-first-out (FIFO) basis. Here’s how you can use them:

// Stack in Java
Stack<Integer> stack = new Stack<>();

// Pushing elements onto the stack

// Popping element from the stack
int lastElement = stack.pop();

// Queue in Python
from collections import deque
queue = deque()

// Adding elements to the queue

// Removing element from the queue
firstElement = queue.popleft()

Both stacks and queues are crucial for tasks that involve reversing items or processing them in a particular order. Consider the following examples:

// Using Stack to reverse a string in Java
Stack<Character> charStack = new Stack<>();
String str = "Zenva";
for (char ch : str.toCharArray()) {
String reversed = "";
while (!charStack.isEmpty()) {
    reversed += charStack.pop();

// Using Queue to simulate a task line in Python
tasks = deque()
tasks.append('Send emails')
tasks.append('Write report')
while tasks:
    current_task = tasks.popleft()
    print(f"Handling task: {current_task}")

In the next section, we’ll build upon these examples and explore more complex data structures such as trees and graphs, which are essential for representing hierarchical data and networked information respectively.

Trees are hierarchical data structures that represent data in a branching structure. Each element in a tree, called a node, has a value and references to other nodes, which are termed as children. The topmost node is known as the root, and any node without children is called a leaf. A common tree structure is the binary tree, where each node has at most two children nodes.

// Defining a class for a binary tree node in Java
class TreeNode {
    int value;
    TreeNode left;
    TreeNode right;

    TreeNode(int value) {
        this.value = value;
        left = null;
        right = null;

// Creating a simple binary tree with a root and two children
TreeNode root = new TreeNode(10);
root.left = new TreeNode(5);
root.right = new TreeNode(20);

Binary trees often are used in implementing binary search trees (BSTs), where for each node, the left children are less than the node, and the right children are greater. This property provides an efficient way to store and retrieve elements maintaining order.

// A method to insert a value in a binary search tree in Java
public TreeNode insert(TreeNode root, int value) {
    if (root == null) {
        return new TreeNode(value);
    if (value < root.value) {
        root.left = insert(root.left, value);
    } else if (value > root.value) {
        root.right = insert(root.right, value);
    return root;

// Inserting values into a BST
TreeNode bstRoot = insert(null, 10);
insert(bstRoot, 5);
insert(bstRoot, 15);

Traversal methods such as in-order, pre-order, and post-order define how to visit nodes in a tree. Here’s an in-order traversal that prints the nodes of a binary tree in a sorted manner:

// In-order traversal of a binary tree in Java
public void inOrderTraversal(TreeNode node) {
    if (node != null) {

// Performing in-order traversal

Graphs, on the other hand, consist of a set of nodes (or vertices) connected by edges. This data structure can represent complex networks, like social relationships or interconnected roads in a map. Graphs can either be directed or undirected depending on whether their edges have a direction.

Creating a simple graph structure often involves defining nodes and their neighbors:

// A simple graph representation in Python using a dictionary
graph = {
    'A' : ['B', 'C'],
    'B' : ['A', 'D', 'E'],
    'C' : ['A', 'F'],
    'D' : ['B'],
    'E' : ['B', 'F'],
    'F' : ['C', 'E']

// Function to add an edge to an undirected graph
def add_edge(graph, node1, node2):

// Adding an edge between two nodes
add_edge(graph, 'A', 'D')

Exploring a graph to find specific nodes or paths can be accomplished with algorithms like depth-first search (DFS) or breadth-first search (BFS). Here’s how you might implement a simple DFS:

// DFS implementation in Python
def dfs(graph, node, visited=None):
    if visited is None:
        visited = set()
    for neighbour in graph[node]:
        if neighbour not in visited:
            dfs(graph, neighbour, visited)

// Executing DFS starting from 'A'
dfs(graph, 'A')

These data structures are the backbone of many complex algorithms and systems. Mastery over them enables you to think critically about solving problems computationally. As you progress in your studies, you’ll find these structures in applications ranging from database indexing to AI. Hands-on experience with these structures and their respective algorithms will significantly bolster your coding proficiency and technical skill set.

Remember that at Zenva, we firmly believe that the best way to learn is by doing. So we encourage you to modify these examples, break them apart, and see how they behave with different data. Experimenting with data structures through coding exercises is the surest way to grasp their nuances and power. Keep coding, and you’ll soon be crafting efficient, elegant solutions for a world of programming challenges!

In the realm of data structures, there are more complex types that cater to specific needs, like handling associative data or prioritizing elements. Let’s look at some of these along with practical code examples.

Maps or Dictionaries: Maps, also known as dictionaries in some languages like Python, are collections of key-value pairs. They are excellent for associative data where you need to retrieve values based on a specific key quickly.

// Creating and using a HashMap in Java
HashMap<String, Integer> ageMap = new HashMap<>();
ageMap.put("Alice", 30);
ageMap.put("Bob", 25);

// Accessing a value using a key
int aliceAge = ageMap.get("Alice");
System.out.println("Alice's age: " + aliceAge);

// Dictionary in Python
ages = {"Alice": 30, "Bob": 25}
print("Bob's age:", ages["Bob"])

Hash Sets: Sets are collections that only allow unique elements. Hash sets specifically operate based on a hash table, providing quick operations to check if an element is present.

// HashSet in Java
HashSet<Integer> uniqueNumbers = new HashSet<>();
uniqueNumbers.add(1); // This will not be added, as it's a duplicate

// Checking if HashSet contains a number
boolean containsTwo = uniqueNumbers.contains(2);
System.out.println("Set contains 2: " + containsTwo);

// Set in Python
unique_nums = {1, 2, 1}  # The second '1' will be ignored
print("Set contains 3?", 3 in unique_nums)

Priority Queues: Priority queues are similar to regular queues but elements are processed based on their priority instead of the order they are added. They are often implemented using a data structure called a binary heap.

// Priority Queue in Java
PriorityQueue<Integer> priorityQueue = new PriorityQueue<>();

// Retrieving elements based on priority (Natural order)
while (!priorityQueue.isEmpty()) {

// Using heapq in Python for a priority queue
import heapq
heap = []
heapq.heappush(heap, 10)
heapq.heappush(heap, 5)
heapq.heappush(heap, 20)
while heap:

Linked Lists: A linked list is a sequence of nodes where each node points to the next node in the sequence. Unlike arrays, elements are not stored contiguously, allowing for efficient insertions and deletions.

// Linked List in Java
LinkedList<Integer> linkedList = new LinkedList<>();
linkedList.addFirst(2); // Insert at the beginning
linkedList.addLast(3);  // Insert at the end

// Accessing elements
int firstElement = linkedList.getFirst();
System.out.println("First Element: " + firstElement);

// Linked list operations in Python
class Node:
    def __init__(self, data):
        self.data = data
        self.next = None

class LinkedList:
    def __init__(self):
        self.head = None

# Add new node at the beginning
def insert_at_beginning(self, data):
    new_node = Node(data)
    new_node.next = self.head
    self.head = new_node

# Traversing a linked list
def display(self):
    current = self.head
    while current:
        current = current.next

# Initializing a linked list and adding elements
ll = LinkedList()

Each data structure has its unique use cases and trade-offs. For instance, while hash maps provide quick access to elements, they don’t preserve any order. Linked lists offer efficient insertion and deletion performance, but accessing an element requires sequential traversal.

Understanding the properties and operations of various data structures will significantly enhance your capacity to choose the right tool for the job. Always keep in mind the complexity of operations when selecting a data structure for a particular task, as this will affect the overall performance of your application.

In our courses at Zenva, we emphasize hands-on learning through practice, because we know that applying these concepts in real coding challenges is the best way to solidify your understanding. So, take these examples, play around with them, and start thinking about how you can use these data structures in your projects!

Continuing Your Journey in Data Structures with Python

Embarking on a learning journey through data structures has set you up with a priceless skill set that can be applied to virtually any programming task. As you’ve discovered, mastering these skills opens up a world of possibilities, whether you’re optimizing algorithms, tackling software engineering problems, or data wrangling. To keep growing your expertise in programming and data structures, it’s essential to practice and continue learning with structured and comprehensive materials.

We invite you to check out our Python Mini-Degree, where you can further hone your coding skills and explore additional aspects of Python programming. This suite of courses is designed to take you from the basics to more advanced topics, allowing you to step up your game in the Python ecosystem, which is renowned for its role in data science, game development, and web applications.

If you’re looking for a broader array of programming knowledge, our collection of Programming courses has you covered. Our courses are crafted to fit your skill level and interests, whether you are just starting out or looking to specialize in a new area. With Zenva, you’ll gain tangible experience by creating projects you can showcase, all the while learning at your own pace within a supportive community of over one million developers. Continue building your skills with us, and take your next step towards a successful career in the tech industry.


By now, it should be clear that data structures are more than just a tool; they are the building blocks that form the foundation of efficient and scalable code. As we’ve explored together, each data structure has its unique strengths and ideal use cases. We hope this tutorial has sparked your curiosity and motivated you to dive deeper into the fascinating world of data structures. By embracing these concepts, you’re equipping yourself with the knowledge and skills to solve an array of programming problems with confidence and finesse.

We at Zenva believe that practical knowledge is key to unlocking your potential as a developer. That’s why our Python Mini-Degree is designed from the ground up to provide you with hands-on experience, in-demand skillsets, and real-world project-building opportunities. Whether your goal is to advance your career, launch a new one, or simply become a better programmer, continuing your education with us is a step in the right direction. Embrace the challenge, and let’s code the future together! Explore our Python Programming Mini-Degree to keep the momentum going!

Did you come across any errors in this tutorial? Please let us know by completing this form and we’ll look into it!

Python Blog Image

FINAL DAYS: Unlock coding courses in Unity, Godot, Unreal, Python and more.