So far, Python has been dealing with one thing at a time.
One name.
One number.
One answer.
That’s fine for small programs.
But real programs need to remember lots of things.
That’s where lists come in.
A list is Python saying:
“I’ll keep all of these together for you.”
What Is a List?
A list is a collection of values stored under one name.
Instead of this:
item1 = "apple"
item2 = "banana"
item3 = "orange"
You write this:
shopping_list = ["apple", "banana", "orange"]
One variable.
Three items.
Much cleaner.
Creating Your First List
Lists are written using square brackets [].
numbers = [1, 2, 3, 4, 5]
names = ["Alex", "Sam", "Jamie"]
A list can hold:
Numbers
Strings
Or a mix of both
mixed = ["Python", 3, True]
Python doesn’t mind.
Lists Are Ordered
Order matters in lists.
colors = ["red", "green", "blue"]
Python remembers:
"red"is first"green"is second"blue"is third
That order will matter when we start accessing items.
Lists Can Change (This Is Important)
Lists are mutable, which is a fancy way of saying:
“You can change them.”
You can:
Add items
Remove items
Replace items
That flexibility is what makes lists so useful.
Adding Items to a List
To add something to the end of a list, use .append().
animals = ["cat", "dog"]
animals.append("hamster")
print(animals)
Output:
['cat', 'dog', 'hamster']
Python just tacked it onto the end.
Removing Items from a List
To remove an item by value, use .remove().
animals.remove("dog")
print(animals)
Now "dog" is gone.
Important note:
Python removes the first matching item it finds.
Lists and Loops: Best Friends
Lists really shine when combined with loops.
fruits = ["apple", "banana", "cherry"]
for fruit in fruits:
print(fruit)
Python goes through the list one item at a time.
This is one of the most common patterns in Python.
A Friendly Example
tasks = ["wake up", "eat", "code", "sleep"]
for task in tasks:
print(f"Don't forget to {task}.")
Simple.
Readable.
Powerful.
Checking How Many Items Are in a List
Use len() to count items.
numbers = [10, 20, 30, 40]
print(len(numbers))
Output:
4
Python counts for you.
Common Beginner Mistakes (Totally Normal)
Mistake 1: Forgetting brackets
numbers = 1, 2, 3 # Not a list
Always use [].
Mistake 2: Expecting lists to stay fixed
Lists are meant to change.
If you want something fixed, that’s coming next.
What You’ve Learned
You now know:
What a list is
How to create one
How to add items
How to remove items
How to loop through a list
Why lists are so useful
This is a big step toward real-world programs.
Mini Quiz
Try these:
What symbol do lists use?
Can a list hold different types of values?
What does
.append()do?What does
len()return?What will this print?
items = ["a", "b"]
items.append("c")
print(items)
Coming Up Next
Now that Python can store many things,
we need to learn how to find specific ones.