Lists

What You Will Learn

A list stores multiple values in a single variable. Instead of creating ten separate variables for ten names, you create one list.

Creating a List

Use square brackets, with items separated by commas:

fruits = ["apple", "banana", "cherry"]
numbers = [1, 2, 3, 4, 5]
mixed = ["Alice", 25, True, 3.14]
empty = []

print(fruits)
print(len(fruits))

Expected output:

['apple', 'banana', 'cherry']
3

Lists can hold any type of value, including a mix of types.

Accessing Items

Use the index (starting at 0):

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

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

Modifying Items

Lists are mutable — you can change them after creation:

fruits = ["apple", "banana", "cherry"]
fruits[1] = "blueberry"
print(fruits)

Expected output:

['apple', 'blueberry', 'cherry']

Common List Methods

Adding Items

fruits = ["apple", "banana"]

fruits.append("cherry")      # add to end
print(fruits)

fruits.insert(1, "blueberry")  # insert at index 1
print(fruits)

Expected output:

['apple', 'banana', 'cherry']
['apple', 'blueberry', 'banana', 'cherry']

Removing Items

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

fruits.remove("banana")   # removes first occurrence
print(fruits)

popped = fruits.pop()     # removes and returns last item
print(popped)
print(fruits)

Expected output:

['apple', 'cherry', 'banana']
banana
['apple', 'cherry']

Sorting

numbers = [3, 1, 4, 1, 5, 9, 2, 6]
numbers.sort()
print(numbers)

words = ["banana", "apple", "cherry"]
words.sort()
print(words)

Expected output:

[1, 1, 2, 3, 4, 5, 6, 9]
['apple', 'banana', 'cherry']

Looping Over a List

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

for fruit in fruits:
    print(f"I like {fruit}")

Expected output:

I like apple
I like banana
I like cherry

Checking if an Item Exists

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

if "banana" in fruits:
    print("We have bananas!")

if "mango" not in fruits:
    print("No mangoes.")

Expected output:

We have bananas!
No mangoes.

List Slicing

Like strings, you can slice a list:

numbers = [0, 1, 2, 3, 4, 5]

print(numbers[1:4])   # [1, 2, 3]
print(numbers[:3])    # [0, 1, 2]
print(numbers[3:])    # [3, 4, 5]

What You Learned

• Lists store multiple values in one variable
• Access items with [index], starting at 0
• Lists are mutable — you can add, remove, and change items
• Common methods: .append(), .insert(), .remove(), .pop(), .sort()
• Use in to check if an item exists

In the next lesson, you will learn about dictionaries — a way to store data as key-value pairs.