5.1 The Power of Lists

The Problem with Single Variables

Imagine you wanted to store a list of your favourite movies. With the tools we have so far, it would be very clumsy:

movie1 = "The Matrix"
movie2 = "Dune"
movie3 = "Blade Runner 2049"
# ... what if you have 100 favourite movies? This is a nightmare!

We need a better way to store and manage a collection of related items. The solution is a data structure, and Python's most common and useful one is the list.

What is a List?

A list is a single variable that can hold an ordered collection of multiple items. Key features are:

• Ordered: The items are stored in a specific sequence that doesn't change.
• Mutable: You can change the list after it's created—add items, remove items, or change existing items.
• Flexible: A single list can hold different data types (though it's most common to have a list of all the same type).

The Syntax: Square Brackets []

We create lists using square brackets, with individual items separated by commas.

# An empty list
shopping_list = []

# A list of strings
favourite_movies = ["The Matrix", "Dune", "Blade Runner 2049"]

# A list of integers
high_scores = [1050, 980, 875, 800]

# A mixed-type list (less common, but possible)
mixed_list = ["Hello", 100, True]

Knowledge Check: Test Your Syntax!

Before you start experimenting, let's see if you can spot a correctly formatted list. Try the interactive activity below.

Live Example: Creating Lists

Now, see the code in action. The Trinket below defines and prints a few different lists. Run it, then follow the "Your Turn" instructions to create your own list!