Section Overview

In this section, you’ll learn how to work with lists, one of Python’s most useful data structures. Lists allow you to store multiple items in a single variable, making it easier to organize and manage data.

By the end of this section, you should be able to:

• Create and manipulate lists
• Access list items using indexing
• Use common list methods to add, remove, and modify items
• Iterate over lists with loops

Lesson 1: Creating Lists

A list is created by placing items inside square brackets, separated by commas.

Example:

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

Output:

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

Lists can hold items of different types, but usually contain related data:

mixed = [1, "two", 3.0, True]

Lesson 2: Accessing Items by Index

List items have positions, starting at 0.

Example:

colors = ["red", "green", "blue"]
print(colors[0])  # Outputs: red print(colors[2])  # Outputs: blue 

Negative indexes count from the end:

print(colors[-1])  # Outputs: blue 

Lesson 3: Common List Methods

• append(item) – add an item to the end
• insert(index, item) – insert an item at a specific position
• remove(item) – remove the first occurrence of an item
• pop() – remove and return the last item
• len(list) – get the number of items

Example:

numbers = [10, 20, 30]
numbers.append(40)
numbers.insert(1, 15)
numbers.remove(20)
last = numbers.pop()
print(numbers)  # Outputs: [10, 15, 30] print(last)     # Outputs: 40 print(len(numbers))  # Outputs: 3 

Lesson 4: Looping Through Lists

You can loop through all items in a list using a for loop:

names = ["Alice", "Bob", "Charlie"]

for name in names:
    print("Hello, " + name)

This prints a personalized greeting for each name.

Quiz: Check Your Understanding

1. What index does the first item in a list have?
Answer: 0

2. Which method adds an item to the end of a list?
Answer: append()

3. What does this code print?

items = [1, 2, 3]
print(items[-2])

Answer: 2

4. True or False: Lists can contain items of different data types.
Answer: True

Practice Exercise: Shopping List

Create a program that:

1. Starts with an empty shopping list (an empty list)
2. Asks the user to enter three items to add to the shopping list
3. Adds each item to the list
4. Prints the final shopping list

Starter code:

shopping_list = []

for i in range(3):
    item = input("Enter an item to add to the shopping list: ")
    shopping_list.append(item)

print("Your shopping list:", shopping_list)

Challenge: Let the user enter items until they type "done".