Is Dictionary a Mutable Data Type in Python?


Scott Campbell

In Python, a dictionary is a mutable data type that allows you to store key-value pairs. It is one of the most versatile and widely used data structures in the Python programming language. Let’s explore what exactly it means for a dictionary to be mutable.

Mutable vs Immutable Data Types

Before diving into dictionaries, let’s understand the concept of mutable and immutable data types in Python.

Mutable data types can be modified after they are created. This means that you can change their values, add or remove elements without creating a new instance of the object.

Immutable data types, on the other hand, cannot be modified once they are created. Any attempt to modify an immutable object will result in creating a new instance of the object with the updated value.

Dictionaries in Python

A dictionary in Python is an example of a mutable data type. It is represented by curly braces ({}) and consists of key-value pairs separated by colons (:). The keys must be unique within a dictionary, but the values can be of different types.

To create a dictionary, you can use either curly braces or the built-in dict() function. Here’s an example:

my_dict = {'name': 'John', 'age': 25, 'city': 'New York'}
# or
my_dict = dict(name='John', age=25, city='New York')

Accessing Dictionary Elements

To access elements in a dictionary, you need to use their corresponding keys. You can do this by enclosing the key inside square brackets ([]). For example:

name = my_dict['name']
print(name)  # Output: John

Modifying Dictionary Elements

One of the main characteristics of a mutable data type is the ability to modify its elements. In the case of dictionaries, you can update or add new key-value pairs by assigning a new value to a specific key.

Let’s say we want to update the age of our person in the dictionary:

my_dict['age'] = 26
print(my_dict)  # Output: {'name': 'John', 'age': 26, 'city': 'New York'}

In this example, we assigned a new value of 26 to the key ‘age’ in our dictionary. As dictionaries are mutable, the change is reflected in the original dictionary itself.

Adding and Removing Elements

In addition to modifying existing elements, dictionaries allow you to add and remove key-value pairs dynamically.

To add a new element, simply assign a value to a new key:

my_dict['occupation'] = 'Software Engineer'
print(my_dict)  # Output: {'name': 'John', 'age': 26, 'city': 'New York', 'occupation': 'Software Engineer'}

To remove an element from a dictionary, you can use the del keyword followed by the key:

del my_dict['city']
print(my_dict)  # Output: {'name': 'John', 'age': 26, 'occupation': 'Software Engineer'}


In Python, dictionaries are mutable data types that allow you to store and manipulate key-value pairs. You can modify existing elements, add new ones, or remove them altogether. Being able to modify dictionaries in-place makes them a powerful tool for handling complex data structures and algorithms.

So, the answer to the question “Is Dictionary a Mutable Data Type in Python?” is yes, dictionaries are indeed mutable. Remember this important characteristic of dictionaries when working with them in your Python programs.

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