How Do You Define a Data Structure in Python?


Larry Thompson

In Python, a data structure is a way of organizing and storing data so that it can be accessed and manipulated efficiently. It provides a way to represent the relationships between different pieces of data and allows for efficient storage and retrieval of information.

Types of Data Structures in Python

Python offers several built-in data structures, each with its own advantages and use cases. These include:

  • Lists: A list is an ordered collection of items. It can contain elements of different types and allows for easy modification, insertion, and deletion of elements.
  • Tuples: Similar to lists, tuples are ordered collections of items.

    However, they are immutable, meaning they cannot be modified once created.

  • Dictionaries: Dictionaries are unordered collections that store key-value pairs. They provide fast access to values based on their associated keys.
  • Sets: A set is an unordered collection of unique elements. It allows for efficient membership testing and operations like union, intersection, and difference.

Defining Custom Data Structures

In addition to the built-in data structures, Python also allows you to define your own custom data structures using classes. This gives you the flexibility to create complex data structures that suit your specific needs.

To define a custom data structure in Python, you need to create a class that represents the structure. The class can have attributes (variables) to store the data and methods (functions) to perform operations on the data.

Example: Creating a Stack Data Structure

A stack is a simple data structure that follows the Last-In-First-Out (LIFO) principle. It can be implemented using a list in Python. Let’s define a Stack class:

class Stack:
    def __init__(self):
        self.items = []

    def push(self, item):

    def pop(self):
        if not self.is_empty():
            return self.pop()

    def is_empty(self):
        return len(self.items) == 0

    def peek(self):
        if not self.items[-1]

In the above example, we define a Stack class with methods to push an item onto the stack, pop an item from the stack, check if the stack is empty, and peek at the top item without removing it.


Data structures are essential tools for organizing and manipulating data efficiently in Python. Whether you use built-in data structures like lists and dictionaries or create your own custom data structures, understanding how they work will greatly enhance your ability to solve problems and write efficient code.

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