Python List Comprehension: A Beginner’s Guide

Aditya Daria
4 min readFeb 25, 2023

Picture this: you’re stranded on a deserted island with nothing but a laptop and a thirst for programming. You want to create lists in Python, but you don’t want to write lengthy for loops or complicated conditional statements. What do you do? Fear not, my friend, for Python List Comprehension is here to save the day!

Photo by Marek Okon on Unsplash

With Python List Comprehension, you can create lists with ease and finesse, all while sipping on a coconut and watching the waves crash against the shore. Say goodbye to verbose code and hello to succinct, readable code that will make your fellow castaways green with envy.

What is List Comprehension?

List comprehension is a way to create new lists by applying a transformation to an existing list or sequence. It provides a concise syntax for creating lists in a single line of code. List comprehension is a Pythonic way of expressing a for loop that appends elements to a list.

The syntax for list comprehension is as follows:

new_list = [expression for item in iterable if condition]
  • new_list is the name of the new list that will be created.
  • expression is the transformation that will be applied to each element of the iterable.
  • item is the current element of the iterable that is being transformed.
  • iterable is the list, tuple, or sequence that is being iterated over.
  • condition is an optional condition that filters the elements that are included in the new list.

Example 1: Creating a List of Squares

Suppose we have a list of integers and we want to create a new list that contains the squares of those integers. We can use list comprehension to achieve this in a single line of code:

numbers = [1, 2, 3, 4, 5]
squares = [num**2 for num in numbers]
print(squares) # Output: [1, 4, 9, 16, 25]

In this example, we are applying the transformation num**2 to each element of the numbers list, which results in a new list of squares.

Example 2: Filtering Elements

We can also use list comprehension to filter elements based on a condition. Suppose we have a list of integers and we want to create a new list that only contains the even integers. We can use list comprehension with a condition to achieve this:

numbers = [1, 2, 3, 4, 5]
evens = [num for num in numbers if num % 2 == 0]
print(evens) # Output: [2, 4]

In this example, we are using the condition num % 2 == 0 to filter out the odd integers from the numbers list, resulting in a new list of even integers.

Example 3: Creating a List of Tuples

List comprehension can also be used to create lists of tuples. Suppose we have two lists, one containing names and another containing ages. We can use list comprehension to create a new list of tuples that contains the name and age of each person:

names = ['Alice', 'Bob', 'Charlie']
ages = [25, 30, 35]
people = [(name, age) for name, age in zip(names, ages)]
print(people) # Output: [('Alice', 25), ('Bob', 30), ('Charlie', 35)]

In this example, we are using the zip function to combine the names and ages lists into a list of tuples. The list comprehension then applies the transformation (name, age) to each tuple in the new list.

Example 4: Comparing List Comprehension and for loops

  • Using a for loop to create a list of even numbers from 0 to 10
even_numbers = []
for x in range(11):
if x % 2 == 0:
even_numbers.append(x)
print(even_numbers)
  • Using list comprehension to create a list of even numbers from 0 to 10
even_numbers = [x for x in range(11) if x % 2 == 0]
print(even_numbers)

As you can see, both the for loop and the list comprehension achieve the same output. However, the list comprehension is more concise and readable. It allows you to create a new list and apply a conditional filter to the list elements in one line of code. This makes your code shorter, easier to read and more efficient.

In summary, the benefits of using list comprehension in Python are:

  • Concise and readable code
  • More efficient than using a for loop with append statements
  • Provides a way to filter elements based on a condition
  • Can be used to create lists of tuples in a single line of code

Conclusion

So there you have it, folks! Python List Comprehension is the ultimate survival tool for all your programming needs. Whether you’re stranded on a deserted island or just trying to write more efficient code, list comprehension will help you get the job done with style and grace. So go forth, my friends, and create those lists with reckless abandon! Who knows, you may just end up building the next big thing in Python…or at least impressing your co-workers with your newfound coding prowess.

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