How to Get Rid of Nested For Loops in Python

Are you tired of writing and dealing with multiple nested for loops in Python? Do you find it confusing and keep on getting entangled in the web of loops and conditions you have written?

Loops improve productivity, but nested loops can create confusion and make the code less readable. This is exactly why you should aim to get rid of nested for loops in Python whenever possible. Today in this tutorial you will learn how to accomplish exactly that.

Understanding Nested For Loops

Before jumping into how to get rid of nested loops, let’s take a moment to understand what a nested for loop is. In Python, you can place a for loop inside another for loop, creating what’s known as a nested loop.

It is a way of approaching a repeated task, and although useful in many scenarios, it is often overused, leading to clumsy code that is difficult to read, understand, and maintain.

Here’s an example of a nested loop:

Use List Comprehensions

We can avoid using nested for loops in Python by using a technique called list comprehension. List comprehension is a complete substitute for the for loop if you’re creating a list. It’s Python’s way of implementing a well-known notation for sets in mathematics. List comprehensions are a way of achieving Pythonic one-liners.

Here’s how we can use list comprehension to flatten a 2D matrix:

Using Map and Lambda Functions

Map and lambda functions can also be used to avoid nested for loops in Python. The map() function executes a specified function for each item in an iterable. The item is sent to the function as a parameter.

The lambda function is a small anonymous function. It can take any number of arguments, but can only have one expression.

Here’s an example:

Displaying the Full Code

Here is an example of code transformation from nested loops into list comprehension.

# nested for loop
output = []
for i in range(3):
    for j in range(3):
        output.append((i, j))

# equivalent list comprehension
output = [(i, j) for i in range(3) for j in range(3)]

Conclusion

Getting rid of nested for loops in Python enhances the readability and maintainability of your code. Python provides several techniques such as list comprehensions and map and lambda functions which can greatly simplify your code. Try to use them whenever possible to keep your code clean, efficient, and Pythonic.