What is List in Python?

Learn about the fundamental concept of lists in Python programming, including its definition, creation, and manipulation. This article provides a step-by-step explanation, code snippets, and practical …

Updated July 23, 2023

Definition

In Python, a list is a collection of items that can be of any data type, including strings, integers, floats, and other lists. Lists are denoted by square brackets [] and are ordered, meaning that each item has an index or position in the list.

Step-by-Step Explanation

Here’s a step-by-step breakdown to help you understand how to work with lists:

Creating a List

To create a list in Python, simply enclose items within square brackets:

my_list = [1, 2, 3, 4, 5]

This creates a list my_list containing the integers 1 through 5.

Accessing List Elements

You can access individual elements of a list using their index (position). Indexes start at 0, so:

print(my_list[0])  # prints 1
print(my_list[2])  # prints 3

Note that attempting to access an element outside the valid index range will result in an IndexError.

Modifying List Elements

You can modify individual elements of a list by assigning a new value:

my_list[0] = 'a'
print(my_list)  # prints ['a', 2, 3, 4, 5]

Adding New Elements

You can add new elements to the end of a list using the append() method:

my_list.append('new_element')
print(my_list)  # prints ['a', 2, 3, 4, 5, 'new_element']

Removing Elements

You can remove an element from a list by its index or value using the remove() and pop() methods:

my_list.remove(4)
print(my_list)  # prints ['a', 2, 3, 5, 'new_element']

my_list.pop()  # removes and returns the last element
print(my_list)  # prints ['a', 2, 3, 5]

Practical Example

Let’s create a simple list-based program that calculates the sum of squares for a given range:

def sum_of_squares(n):
    my_list = []
    for i in range(1, n+1):
        my_list.append(i ** 2)
    return sum(my_list)

print(sum_of_squares(5))  # prints the sum of squares from 1 to 5

Conclusion

In this article, we explored the fundamental concept of lists in Python programming. You learned how to create, access, modify, add new elements, and remove elements from a list. With practice, you’ll become comfortable working with lists and take advantage of their versatility in your Python programs.