Are Dictionaries Mutable Python?

are dictionaries mutable python

As a professional Python programmer, I have often come across the question of whether dictionaries are mutable in Python. This question is intriguing because it relates to the fundamental behavior of a key data structure in Python. Mutability refers to the ability of an object to be changed after it has been created. In this section, we will explore the concept of dictionary mutability in Python and its behavior.

Key Takeaways:

  • Python dictionaries are a powerful data structure used for managing and manipulating data.
  • Dictionaries are mutable in Python, meaning they can be modified after they are created.
  • Various methods and operations can be used to modify dictionaries in Python.
  • Understanding dictionary mutability is crucial for efficient data handling in Python programming.
  • Dictionaries are a core component of Python programming, and their behavior is crucial for any programmer to understand.

Modifying Dictionaries in Python

Now that we know dictionaries in Python are mutable, let’s dive into the ways we can modify them. So, can you change dictionaries in Python? Of course! One of the most common ways to change a dictionary is by adding a new key-value pair. This can be done by simply assigning a new value to a new or existing key.


>>> my_dict = {‘apple’: 2, ‘banana’: 4, ‘cherry’: 6}
>>> my_dict[‘orange’] = 8
>>> print(my_dict)
{‘apple’: 2, ‘banana’: 4, ‘cherry’: 6, ‘orange’: 8}

We can also remove a key-value pair from a dictionary using the del keyword, passing in the key to be deleted.


>>> del my_dict[‘banana’]
>>> print(my_dict)
{‘apple’: 2, ‘cherry’: 6, ‘orange’: 8}

Another way to add or modify items in a dictionary is by using the update() method. This method takes a dictionary as an argument and updates the calling dictionary with the key-value pairs from the argument dictionary.


>>> my_dict.update({‘apple’: 3, ‘orange’: 10})
>>> print(my_dict)
{‘apple’: 3, ‘cherry’: 6, ‘orange’: 10}

It is also worth noting that dictionaries are mutable objects in Python. This means that they can be changed in place. Other mutable objects in Python include lists and sets. This is in contrast to immutable objects, like strings and tuples, which cannot be changed once they are created.

In summary, the mutability of dictionaries in Python allows us to easily modify and update their contents. By adding, removing, or updating key-value pairs, we can efficiently manage and manipulate data within a dictionary. Understanding these operations and the concept of mutable objects is essential in becoming proficient in Python programming.

Conclusion: Are Dictionaries Mutable in Python?

In conclusion, after exploring the concept of mutability in Python dictionaries, the answer to the question “Are dictionaries mutable in Python?” is a resounding YES!

Python dictionaries are a powerful data structure that allows for the flexible and efficient management and manipulation of data. The ability to modify dictionaries after they are created is a key characteristic that distinguishes them from other immutable data structures in Python, such as tuples and strings.

Through the use of various methods and operations, such as adding, removing, and updating key-value pairs, dictionaries can be changed and manipulated to suit your needs. This mutability makes them an excellent choice for applications that require dynamic data storage and retrieval.

Overall, understanding the behavior and mutability of dictionaries is essential for effectively leveraging their capabilities in your Python programs. So, next time you come across a situation that requires efficient data management, remember that dictionaries are indeed mutable in Python!


Q: Are dictionaries mutable in Python?

A: Yes, dictionaries in Python are mutable. This means that you can modify their content after they are created.

Q: How can I modify dictionaries in Python?

A: There are several methods and operations that allow you to modify dictionaries in Python. You can use the assignment operator (=) to add or update key-value pairs, the del keyword to remove key-value pairs, and various built-in methods such as update() and pop() to perform specific modifications.

Q: Can I change the keys or values of a dictionary in Python?

A: Yes, you can change both the keys and values of a dictionary in Python. Since dictionaries are mutable, you can reassign new values to existing keys or create new key-value pairs.

Q: What happens if I try to modify a dictionary key that doesn’t exist?

A: If you try to modify a dictionary key that doesn’t exist, Python will automatically add the key-value pair to the dictionary.

Q: Is it possible to make dictionaries immutable in Python?

A: No, dictionaries in Python are inherently mutable. If you need an immutable version of a dictionary, you can consider using the built-in frozenset() function, which creates an immutable dictionary-like object.

Q: Are there any performance implications of modifying dictionaries in Python?

A: Modifying dictionaries in Python can have performance implications, especially when dealing with large dictionaries. As dictionaries grow in size, the time complexity of certain operations such as adding or removing key-value pairs can increase. It’s important to consider the size and complexity of your dictionary when making frequent modifications.

Q: Can I modify a dictionary while iterating over it?

A: Modifying a dictionary while iterating over it can lead to unpredictable behavior. It’s generally recommended to create a copy of the dictionary before modifying it or use a different approach, such as creating a list of keys and iterating over the list instead.

Q: What are some common use cases for modifying dictionaries in Python?

A: Modifying dictionaries in Python is often used in scenarios where you need to update or manage data dynamically. Some common use cases include processing user input, updating database records, and manipulating structured data.

Q: Are there any restrictions on the types of objects that can be used as dictionary keys or values?

A: In Python, dictionary keys must be immutable objects, meaning they cannot be changed after creation. However, dictionary values can be of any type, including mutable objects such as lists or other dictionaries.

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