Python Lists

A List is one of the most important data structures in Python. Lists are used to store multiple values in a single variable.

Why Lists are Important?

Creating a List

Lists are created using square brackets [].

numbers = [10, 20, 30, 40]

print(numbers)

Output

[10, 20, 30, 40]

Here:

Lists can Store Different Data Types

data = [10, "Python", 99.5, True]

print(data)

Output

[10, 'Python', 99.5, True]

Python lists can store integers, strings, floats, and boolean values together.

List Indexing

Each element in a list has an index number. Indexing starts from 0.

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

print(fruits[0])

print(fruits[1])

print(fruits[2])

Output

Apple
Mango
Orange

Explanation:

Negative Indexing

Negative indexing starts from the end of the list.

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

print(fruits[-1])

print(fruits[-2])

Output

Orange
Mango

List Slicing

Slicing is used to get multiple elements from a list.

numbers = [10, 20, 30, 40, 50]

print(numbers[1:4])

Python starts from index 1 and stops before index 4.

Output

[20, 30, 40]

Changing List Values

Lists are mutable, meaning elements can be modified.

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

fruits[1] = "Banana"

print(fruits)

Output

['Apple', 'Banana', 'Orange']

Adding Elements using append()

append() adds a new element at the end of the list.

numbers = [10, 20, 30]

numbers.append(40)

print(numbers)

Output

[10, 20, 30, 40]

Adding Elements using insert()

insert() adds an element at a specific position.

numbers = [10, 20, 30]

numbers.insert(1, 15)

print(numbers)

Output

[10, 15, 20, 30]

Removing Elements using remove()

remove() deletes a specific element from the list.

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

fruits.remove("Mango")

print(fruits)

Output

['Apple', 'Orange']

Removing Elements using pop()

pop() removes element using index number.

numbers = [10, 20, 30]

numbers.pop(1)

print(numbers)

Output

[10, 30]

Finding List Length

Use len() function to count total elements.

numbers = [10, 20, 30, 40]

print(len(numbers))

Output

4

Looping Through a List

Lists are commonly used with loops.

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

for item in fruits:

    print(item)

Output

Apple
Mango
Orange

Checking if Item Exists

Use the in keyword to check elements.

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

print("Mango" in fruits)

print("Banana" in fruits)

Output

True
False

Sorting a List

sort() arranges elements in ascending order.

numbers = [50, 10, 40, 20]

numbers.sort()

print(numbers)

Output

[10, 20, 40, 50]

Reversing a List

numbers = [10, 20, 30]

numbers.reverse()

print(numbers)

Output

[30, 20, 10]

Copying a List

numbers = [10, 20, 30]

new_list = numbers.copy()

print(new_list)

Output

[10, 20, 30]

Nested Lists

A list inside another list is called nested list.

data = [

    [1, 2],

    [3, 4]
]

print(data)

Output

[[1, 2], [3, 4]]

Real Life Example

This example stores student marks in a list.

marks = [85, 90, 78, 92]

total = sum(marks)

print(total)

average = total / len(marks)

print(average)

Output

345
86.25

Summary