Lists and Arrays

Imagine you want to store the names of 30 students. You could create 30 separate variables — but that would be exhausting and impractical. A list solves this by storing multiple values inside a single variable, in order. In other programming languages this structure is often called an array.

Creating a List

fruits = ["apple", "banana", "cherry"]
scores = [85, 72, 91, 68, 77]
mixed = [1, "hello", True, 3.14]
empty = []

Lists use square brackets []. Items are separated by commas. A list can hold any type of data — even a mix of types.

Accessing Items

Items are accessed by their index, starting at 0:

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

Negative indices count from the end: -1 is the last item, -2 is second to last, and so on.

Modifying a List

Lists are mutable — you can change them after creation:

scores = [70, 80, 90]
scores[1] = 85        # change index 1
print(scores)         # [70, 85, 90]

Adding and Removing Items

Useful List Operations

numbers = [4, 1, 9, 2, 7, 3]
print(len(numbers))         # 6
print(min(numbers))         # 1
print(max(numbers))         # 9
print(sum(numbers))         # 26
print(sorted(numbers))      # [1, 2, 3, 4, 7, 9]
print(9 in numbers)         # True

Iterating Over a List

The most common way to process every item in a list is a for loop:

students = ["Alice", "Bob", "Carlos", "Diana"]
for student in students:
    print(f"Hello, {student}!")

If you also need the index, use enumerate():

for i, student in enumerate(students):
    print(f"{i + 1}. {student}")

List Slicing

Just like strings, lists support slicing:

numbers = [10, 20, 30, 40, 50]
print(numbers[1:4])    # [20, 30, 40]
print(numbers[:3])     # [10, 20, 30]
print(numbers[2:])     # [30, 40, 50]