Lists in Python

Every variable you’ve used so far has held exactly one value. One number, one word, one True/False. But real programs rarely deal with just one thing, you’ve got a class full of students, a week of temperatures, a cart full of items. Storing each of those in a separate variable would be painful. That’s the problem a list solves.

What a list actually is?

A list is a single variable that holds multiple values, in a specific order, and you can add, remove, or change items whenever you want. You create one with square brackets, separating each item with a comma.

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

Output: ['apple', 'banana', 'mango']

A list can hold numbers, strings, even a mix of different types in the same list, though in practice you’ll mostly keep one type per list to stay sane.

numbers = [10, 25, 3, 47]
mixed = ["Nepal", 2026, True]

Accessing items with indexing

Every item in a list has a position, called an index, starting at 0, not 1. This trips up almost everyone at first.

fruits = ["apple", "banana", "mango"]
print(fruits[0])   # apple
print(fruits[1])   # banana
print(fruits[2])   # mango

Python also lets you count backward from the end using negative indexes.

print(fruits[-1])   # mango, the last item
print(fruits[-2])   # banana, second from the end

Changing a value in a list

Unlike strings, lists are mutable, meaning you can change an item after creating the list, without having to build a new one.

fruits = ["apple", "banana", "mango"]
fruits[1] = "orange"
print(fruits)   # ['apple', 'orange', 'mango']

Adding items: append() and insert()

fruits = ["apple", "banana"]
fruits.append("mango")
print(fruits)   # ['apple', 'banana', 'mango']

append() always adds to the end. If you need to add something at a specific position instead, use insert().

fruits.insert(1, "kiwi")
print(fruits)   # ['apple', 'kiwi', 'banana', 'mango']

Removing items: remove(), pop(), and clear()

fruits = ["apple", "banana", "mango"]
fruits.remove("banana")
print(fruits)   # ['apple', 'mango']

remove() deletes by value, not position. If the value doesn’t exist in the list, Python throws an error, so it’s worth checking first if you’re not sure it’s there.

fruits = ["apple", "banana", "mango"]
last_item = fruits.pop()
print(last_item)   # mango
print(fruits)       # ['apple', 'banana']

pop() removes the last item by default, and hands it back to you, which is genuinely useful when you need the removed value for something else. Give it a position, like fruits.pop(0), and it removes that specific item instead.

Looping through a list

You already saw this in the for loop lesson, but it’s worth repeating here since it’s the most common thing you’ll do with a list.

fruits = ["apple", "banana", "mango"]
for fruit in fruits:
    print(fruit)

Checking length and membership

fruits = ["apple", "banana", "mango"]
print(len(fruits))          # 3
print("banana" in fruits)   # True
print("grape" in fruits)    # False

len() tells you how many items are in the list. in Checks whether a value exists inside it, same membership operator you already learned, it just works on lists too, not only strings.

Sorting a list

numbers = [5, 2, 8, 1]
numbers.sort()
print(numbers)   # [1, 2, 5, 8]

numbers.sort(reverse=True)
print(numbers)   # [8, 5, 2, 1]

sort() changes the original list permanently. If you want a sorted copy while keeping the original untouched, use sorted(numbers) instead.

numbers = [4, 8, 15, 16]
print(numbers[-1])
print(numbers[-3])