Day 10: Lists — One Box, Many Things!

What's a List?

So far variables store one thing. name = "Rohith". But what if you have 100 students? You can't make 100 variables! A list is like a train — one train, many compartments. One variable, many values!

Creating a List

fruits = ["Apple", "Mango", "Banana"]

Square brackets [ ] hold the list. Commas separate each item. That's it!

Getting Items From a List

fruits = ["Apple", "Mango", "Banana"]

print(fruits[0])
print(fruits[1])
print(fruits[2])

The number inside [ ] is the position. But remember — lists start counting from 0, not 1! Apple is at position 0, Mango is at 1, Banana is at 2.

Real World Connection

Your Instagram feed is a list of posts. Your WhatsApp contacts is a list of names. Your Swiggy cart is a list of food items. Every collection of things in every app is stored as a list!

Useful List Actions

friends = ["Priya", "Sam", "Arjun"]

friends.append("Rohith")
print(len(friends))
print(friends[0])

append() adds a new item. len() counts how many items. Just like adding a new contact on WhatsApp!

Loop Through a List

fruits = ["Apple", "Mango", "Banana"]

for fruit in fruits:
    print(fruit)

This prints every item automatically. Instagram uses this exact pattern to show every post in your feed!

Common Mistakes

Mistake 1 — Going out of range.

fruits = ["Apple", "Mango", "Banana"]
print(fruits[3])
print(fruits[2])

Mistake 2 — Forgetting the square brackets.

fruits = "Apple", "Mango"
fruits = ["Apple", "Mango"]

Mini Challenge

Quick Quiz

Q: I have a list of 3 items. What's the last item's position? A: Position 2! Lists start from 0, so 3 items = positions 0, 1, 2.

Q: How do you add a new item to a list? A: listname.append("new item")

Q: How do you count how many items are in a list? A: len(listname)

Key Takeaways