Python Q & A


What is list comprehension in Python?

List comprehension is a concise and elegant way to create lists in Python. It provides a more syntactically readable approach to generate lists than using traditional loops. Essentially, list comprehension is a syntactic construct that allows for the creation of a new list by applying an expression to each item in an existing list (or other iterable objects), optionally filtering the results based on certain criteria.

Basic Syntax:


[expression for item in iterable if condition]




  1. Creating a List of Squares:

squares = [x**2 for x in range(10)]

print(squares)  # Output: [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]



  1. Filtering Results: Generate a list of even numbers from 0 to 9.

evens = [x for x in range(10) if x % 2 == 0]

print(evens)  # Output: [0, 2, 4, 6, 8]



  1. Nested List Comprehensions: Flatten a matrix into a single list.

matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

flattened = [num for row in matrix for num in row]

print(flattened)  # Output: [1, 2, 3, 4, 5, 6, 7, 8, 9]




– Readability: List comprehensions can make code more readable, especially for simple transformations and filtering.

– Performance: They are often faster than equivalent `for` loops because of internal optimizations.


While list comprehensions are powerful, they can reduce readability if overused or employed for complex operations. For more intricate scenarios, traditional loops might be a clearer choice.

List comprehensions are a hallmark of Pythonic code, offering a succinct way to generate lists. By understanding and using them effectively, developers can write cleaner, more efficient code while also making their programs more Pythonic in nature.

Previously at
Flag Argentina
time icon
Senior Software Engineer with 7+ yrs Python experience. Improved Kafka-S3 ingestion, GCP Pub/Sub metrics. Proficient in Flask, FastAPI, AWS, GCP, Kafka, Git