List in Python

What Is a List?

A list is an ordered, mutable (changeable) collection that can hold items of any type — even a mix of types. Lists are one of the most frequently used data structures in Python.

fruits = ["apple", "banana", "cherry"]
mixed  = [1, "two", 3.0, True]

Accessing List Items — Indexing

fruits = ["apple", "banana", "cherry"]
print(fruits[0])    # apple  (first item)
print(fruits[-1])   # cherry (last item)

Slicing a List

numbers = [10, 20, 30, 40, 50]
print(numbers[1:3])   # [20, 30]
print(numbers[:2])    # [10, 20]
print(numbers[2:])    # [30, 40, 50]
print(numbers[::-1])  # [50, 40, 30, 20, 10] — reversed

Common List Methods

fruits = ["apple", "banana"]

fruits.append("cherry")     # add to end     → ['apple', 'banana', 'cherry']
fruits.insert(1, "mango")   # insert at index → ['apple', 'mango', 'banana', 'cherry']
fruits.remove("banana")     # remove by value
fruits.pop()                 # remove last item
fruits.sort()                 # sort alphabetically
fruits.reverse()              # reverse the order
print(len(fruits))            # number of items

Looping Through a List

courses = ["Python", "Data Science", "AI"]
for course in courses:
    print(course)

List Comprehension

A concise way to build a list from an existing sequence in a single line:

squares = [x * x for x in range(1, 6)]
print(squares)   # [1, 4, 9, 16, 25]

evens = [x for x in range(10) if x % 2 == 0]
print(evens)      # [0, 2, 4, 6, 8]

Nested Lists

matrix = [[1, 2], [3, 4], [5, 6]]
print(matrix[1][0])   # 3

List vs Tuple vs Set vs Dict — At a Glance

Key Takeaways

• Lists are ordered and mutable — you can add, remove, and change items after creation
• Use indexing (list[0]) and slicing (list[1:3]) to access items
• List comprehensions offer a quick, readable way to build a new list from a sequence