Which Data Type Is Not Mutable in Python?


Larry Thompson

Python is a versatile and powerful programming language known for its simplicity and readability. One of the key features of Python is its support for different data types.

Data types define the nature and characteristics of variables or objects in Python. They help determine how data can be stored, manipulated, and used in a program.

In Python, most data types are mutable, which means they can be modified or changed after they are created. However, there is one data type that stands out from the rest – the tuple.

Unlike other data types such as lists or dictionaries, tuples are immutable. This means that once a tuple is created, its elements cannot be modified.

Let’s take a closer look at tuples and why they are immutable in Python.

Tuples: An Introduction

A tuple is an ordered collection of elements enclosed in parentheses (). Each element within a tuple is separated by commas.

Tuples can contain elements of different data types, including numbers, strings, lists, or even other tuples. Here’s an example to illustrate:

my_tuple = (1, 'hello', [3, 5], ('a', 'b'))

In this example, we have a tuple called my_tuple that contains four elements: the integer 1, the string ‘hello’, the list [3, 5], and another tuple (‘a’, ‘b’). Tuples are commonly used to group related pieces of information together.

Immutability of Tuples

Unlike lists or dictionaries that allow modifications such as appending or changing elements at specific indices, tuples do not support these operations. Once a tuple is created, its elements cannot be modified individually.

For instance, let’s say we have a tuple representing coordinates:

coordinates = (10, 20)

If we try to modify the first element of the tuple to 30 using indexing and assignment, we will encounter an error:

coordinates[0] = 30  # Throws an error

This is because tuples are immutable, and their elements cannot be reassigned or changed directly. If you need to modify a tuple, you have to create a new tuple.

Advantages of Immutable Tuples

While it may seem limiting at first, the immutability of tuples brings several advantages in certain situations. Here are a few reasons why you might choose to use tuples instead of mutable data types:

  • Security: Since tuples are immutable, they are hashable and can be used as keys in dictionaries or elements in sets. This property ensures the integrity of data structures that rely on immutability.
  • Performance: Immutable data types like tuples can be faster in certain scenarios.

    They consume less memory and do not require any additional memory allocations for modifications.

  • Reliability: Immutable objects are thread-safe, meaning multiple threads can safely access them without causing any unexpected behavior or race conditions.
  • Integrity: The immutability of tuples ensures that their values remain consistent throughout their lifetime. This property is especially useful when dealing with configurations, constants, or other scenarios where values should not change.


In Python, most data types are mutable and allow modifications after creation. However, the tuples, represented by parentheses (), stand out as one of the few immutable data types in Python. While this immutability might seem restrictive at first, it brings several benefits such as security, performance optimizations, reliability in multi-threaded environments, and data integrity.

Understanding the immutability of tuples is essential for writing efficient and reliable Python programs. By leveraging their unique properties, you can design more robust and secure applications. So, the next time you encounter a situation where you need to store data that should not be modified, consider using tuples in your Python code.

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