How do you split a list into evenly sized chunks in Python?

Sometimes it is necessary to divide a lengthy list into smaller and easy-to-read data. For example, if you wish to arrange a list of items in groups, it can be helpful to break it into small parts. This is useful for tasks like grouping data for analysis or showing items in a user interface.

Python provides various simple methods to do this. In order to work with smaller data sets without losing any information, this article will show you how to split a list into uniformly sized chunks.

What is List?

List is one of the frequently used data structures in python. A list is a data structure in python that is mutable and has ordered sequence of elements. Following is a list of integer values ?

numbers = [5, 10, 15, 20, 25]
print(numbers)

[5, 10, 15, 20, 25]

Here we can split a list into evenly sized chunks in Python using different ways ?

• Using Slice Operator

• Using Yield Keyword

• Using List Comprehension

• Using Numpy Module

Using Slice Operator

You can split a list into equally sized chunks using the slice operator in a simple loop approach.

Example

In the below example we have divided 10 numbers into 5 equally sized lists ?

numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
chunk_size = 2

for i in range(0, len(numbers), chunk_size):
    chunk = numbers[i:i + chunk_size]
    print(chunk)

[1, 2]
[3, 4]
[5, 6]
[7, 8]
[9, 10]

Using the Yield Keyword

Yield is a Python keyword which is used to return from a function, where it does not forget its local states. When we want to have multiple returns (partial solutions) from a function without exiting the function and without losing its local states we use the yield keyword.

Example 1

The following is an example program to demonstrate the usage of yield keyword to split a list into evenly sized chunks in python ?

def chunks(data, n):
    for i in range(0, len(data), n):
        yield data[i:i + n]

numbers = [10, 20, 30, 40, 50, 60, 70, 80, 90, 100]
chunk_size = 2
result = list(chunks(numbers, chunk_size))
print(result)

[[10, 20], [30, 40], [50, 60], [70, 80], [90, 100]]

Example 2

Here we have defined a function to split the list in the example below. We iterate from 0 to the length of the list using the for loop and range() method, using the size of the chunk as the step ?

def split_list(data, size_of_chunk):
    for i in range(0, len(data), size_of_chunk):
        yield data[i:i + size_of_chunk]

size_of_chunk = 4
the_list = [23, 56, 83, 19, 38, 64, 92, 56]
result = list(split_list(the_list, size_of_chunk))
print('The even size chunk list is as follows:', result)

The even size chunk list is as follows: [[23, 56, 83, 19], [38, 64, 92, 56]]

Using List Comprehension

List comprehension provides shorter syntax and allows to create new lists from other iterables like tuples, lists, strings, arrays etc.

Example

The following is an example program to split a list into evenly sized chunks in python using the list comprehension ?

numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9]
chunk_size = 3
chunks = [numbers[i:i + chunk_size] for i in range(0, len(numbers), chunk_size)]
print(chunks)

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

Using Numpy Module

NumPy is a general-purpose package for handling arrays in Python. It offers a multidimensional array object with outstanding speed as well as tools for interacting with these arrays.

Example

We have a array_split() method of NumPy which divides a list into chunks. Here, we split the list into 4 chunks ?

import numpy as np

numbers = [23, 56, 83, 19, 38, 64, 92, 56]
chunks = np.array_split(numbers, 4)
print('The evenly sized chunk list is:', chunks)

The evenly sized chunk list is: [array([23, 56]), array([83, 19]), array([38, 64]), array([92, 56])]

Comparison

Conclusion

Python offers multiple approaches to split lists into evenly sized chunks. Use list comprehension for readable one-liners, yield for memory-efficient processing of large lists, and NumPy for numerical data operations.