What is the difference between a list and a tuple in Python?

Q: What is the difference between a list and a tuple in Python?

Learn the answer to "What is the difference between a list and a tuple in Python?" with detailed explanations, code examples, and best practices on DeployU.

The Scenario

You are a backend engineer at a social media company. You are writing a new service that needs to store a collection of items. You are not sure whether to use a list or a tuple to store the items.

The Challenge

Explain the difference between a list and a tuple in Python. What are the pros and cons of each approach, and which one would you choose for this use case?

Wrong Approach

A junior engineer might think that they are interchangeable. They might not be aware of the difference in mutability or the performance implications of choosing one over the other.

Addresses symptoms, not root cause

Right Approach

A senior engineer would be able to provide a detailed explanation of the differences between lists and tuples. They would also be able to explain the trade-offs between each approach and would have a clear recommendation for which one to use in this use case.

Step 1: Understand the Key Differences

Feature	List	Tuple
Mutability	Mutable, can be changed after it is created.	Immutable, cannot be changed after it is created.
Syntax	`[1, 2, 3]`	`(1, 2, 3)`
Performance	Slower than tuples.	Faster than lists.
Use Cases	When you need a collection of items that can be changed.	When you need a collection of items that should not be changed.

Step 2: Choose the Right Tool for the Job

For our use case, it depends on whether we need to be able to change the collection of items after it is created.

If we need to be able to add or remove items from the collection, we should use a list.
If the collection of items will not change, we should use a tuple.

Step 3: Code Examples

Here are some code examples that show the difference between the two approaches:

List:

my_list = [1, 2, 3]
my_list.append(4)
print(my_list) # [1, 2, 3, 4]

Tuple:

my_tuple = (1, 2, 3)
# This will raise an error, because tuples are immutable
# my_tuple.append(4)

Systematic, production-ready debugging

Practice Question

You want to use a collection of items as a key in a dictionary. Which of the following would you use?

Questions