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+---- Thread: CHAPTER 12 — Lists: Storing Multiple Items (/showthread.php?tid=230)
CHAPTER 12 — Lists: Storing Multiple Items - Leejohnston - 11-15-2025
Chapter 12 — Lists: Storing Multiple Items
Lists let you store many values in one variable — the foundation of real-world coding.
A list is like a container that holds multiple items:
Code:
fruits = ["apple", "banana", "cherry"]Each item has an index:
• apple → index 0
• banana → index 1
• cherry → index 2
---
12.1 Creating Lists
Code:
numbers = [10, 20, 30]
names = ["Mia", "Lee", "Johno"]
mixed = ["text", 42, 3.14, True]Python allows mixed types — but good practice is to keep lists consistent.
---
12.2 Accessing Items
Use square brackets:
Code:
fruits = ["apple", "banana", "cherry"]
print(fruits[0]) # apple
print(fruits[2]) # cherryIndexes start at 0.
---
12.3 Changing Items
Code:
fruits[1] = "mango"
print(fruits)---
12.4 Adding Items
append() → add to the end:
Code:
fruits.append("orange")insert() → add to a specific position:
Code:
fruits.insert(1, "kiwi")---
12.5 Removing Items
remove() → remove by value:
Code:
fruits.remove("banana")pop() → remove by index:
Code:
fruits.pop(0) # removes first itemRemove last item:
Code:
fruits.pop()---
12.6 Checking Length
Code:
print(len(fruits))---
12.7 Looping Through a List
Code:
for fruit in fruits:
print(fruit)---
12.8 Slicing Lists
Code:
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]---
12.9 Sorting Lists
Sort alphabetically or numerically:
Code:
numbers.sort()
names.sort()Reverse:
Code:
numbers.reverse()---
12.10 Checking for an Item
Code:
if "apple" in fruits:
print("Apple is here!")---
12.11 Copying Lists (Important)
If you want a REAL copy:
Code:
new_list = old_list.copy()If you do this:
Code:
new_list = old_listThey become linked — changing one changes the other.
---
12.12 List of Lists
Lists can contain other lists:
Code:
matrix = [
[1, 2, 3],
[4, 5, 6],
[7, 8, 9]
]Access:
Code:
print(matrix[1][2]) # 6---
12.13 Mini Project — To-Do List
Write a program that:
• starts with an empty list
• asks the user for 3 tasks
• appends them
• prints the final list
---
12.14 Challenge — Shopping Cart System
Ask the user to enter items until they type “done”.
Store them in a list.
Then:
• display number of items
• sort the list
• print each item on a new line
Example:
Code:
Your cart contains:
• apples
• bread
• milk---
12.15 Chapter Summary
• lists store multiple values
• indexes start at 0
• append() adds to the end
• remove() and pop() delete items
• slices extract parts of lists
• sort(), reverse(), and len() are essential
• loops work beautifully with lists
• lists can store ANY type
Next:
Chapter 13 — Dictionaries: Storing Information With Keys
Dictionaries let you store data in a structured way, just like a database.
---
Written and Compiled by Lee Johnston — Founder of The Lumin Archive