Data Structures - Lists and Tuples

Collections of Data

Up until now, we’ve stored single values in variables. But in the real world, we often deal with collections: a list of users, a series of temperatures, or a shopping cart.

Python provides several built-in Data Structures to handle collections. Today we’ll cover the two most common ones: Lists and Tuples.

Python Lists

A List is an ordered, changeable collection of items. In Python, lists are written with square brackets [].

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fruits = ["apple", "banana", "cherry"]
numbers = [1, 2, 3, 4, 5]
mixed = ["hello", 10, True] # Lists can store different types

Indexing and Slicing

Items in a list are indexed starting from 0.

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fruits = ["apple", "banana", "cherry"]

print(fruits[0])  # Output: apple
print(fruits[-1]) # Output: cherry (last item)

# Slicing: [start:stop]
print(fruits[0:2]) # Output: ["apple", "banana"]

Modifying Lists

Lists are mutable, meaning you can change them after they are created.

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fruits = ["apple", "banana"]

fruits.append("orange")   # Add to end
fruits.insert(1, "kiwi") # Add at index 1
fruits.remove("apple")    # Remove specific item
pop_item = fruits.pop()   # Remove and return last item

fruits[0] = "strawberry"  # Change item at index 0

Python Tuples

A Tuple is similar to a list, but it is immutable—it cannot be changed after creation. Tuples are written with parentheses ().

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coordinates = (10, 20)
dimensions = (1920, 1080)

# dimensions[0] = 800 # This would cause an ERROR!

Why use Tuples?

1. Safety: Use them for data that should never change (like GPS coordinates).
2. Performance: Tuples are slightly faster than lists.
3. Dictionary Keys: Tuples can be used as keys in dictionaries (which we’ll learn tomorrow).

Interactive Practice

Try creating a list of your top 3 favorite movies, then add a 4th one to the list.