In this article, we will cover how we split a list into evenly sized chunks in Python.
Below are the methods that we will cover:
- Using yield
- Using for loop in Python
- Using List comprehension
- Using Numpy
- Using itertool
Method 1: Break a list into chunks of size N in Python using yield keyword
The yield keyword enables a function to come back where it left off when it is called again. This is the critical difference from a regular function. A regular function cannot comes back where it left off. The yield keyword helps a function to remember its state. The yield enables a function to suspend and resume while it turns in a value at the time of the suspension of the execution.
Python3
my_list = ['Lazyroar', 'for', 'Lazyroar', 'like', 'geeky','nerdy', 'geek', 'love', 'questions','words', 'life'] # Yield successive n-sized# chunks from l.def divide_chunks(l, n): # looping till length l for i in range(0, len(l), n): yield l[i:i + n] # How many elements each# list should haven = 5 x = list(divide_chunks(my_list, n))print (x) |
Output:
[['Lazyroar', 'for', 'Lazyroar', 'like', 'geeky'], ['nerdy', 'geek', 'love', 'questions', 'words'], ['life']]
Time Complexity: O(n)
Auxiliary Space: O(1)
Method 2: Break a list into chunks of size N in Python using a loop
In this example, we are using a loop in python and list slicing that will help us to break a list into chunks.
Python3
my_list = [1, 2, 3, 4, 5, 6, 7, 8, 9]start = 0end = len(my_list)step = 3for i in range(start, end, step): x = i print(my_list[x:x+step]) |
Output:
[1, 2, 3] [4, 5, 6] [7, 8, 9]
Time Complexity: O(n)
Auxiliary Space: O(n), where n is length of list
Method 3: Break a list into chunks of size N in Python using List comprehension
It is an elegant way to break a list into one line of code to split a list into multiple lists in Python.
Python3
my_list = [1, 2, 3, 4, 5, 6, 7, 8, 9] # How many elements each# list should haven = 4 # using list comprehensionfinal = [my_list[i * n:(i + 1) * n] for i in range((len(my_list) + n - 1) // n )] print (final) |
Output:
[[1, 2, 3, 4], [5, 6, 7, 8], [9]] Auxiliary Space: O(1)
Alternate Implementation :
Python3
l = [1, 2, 3, 4, 5, 6, 7, 8, 9] # How many elements each # list should have n = 4 # using list comprehension x = [l[i:i + n] for i in range(0, len(l), n)] print(x) |
Output:
[[1, 2, 3, 4], [5, 6, 7, 8], [9]]
Method 4: Break a list into chunks of size N in Python using Numpy
Here, we are using a Numpy.array_split, which splits the array into n chunks of equal size.
Python3
import numpy as np arr = range(30)np.array_split(arr, 6) |
Output:
[array([0, 1, 2, 3, 4]), array([5, 6, 7, 8, 9]), array([10, 11, 12, 13, 14]), array([15, 16, 17, 18, 19]), array([20, 21, 22, 23, 24]), array([25, 26, 27, 28, 29])]
Method 5: Break a list into chunks of size N in Python using itertool
In this example, we will use itertool to slice each array in equal size. we are passing a parameter in the range of 30 and split size of 5.
Python3
from itertools import islice def chunk(arr_range, arr_size): arr_range = iter(arr_range) return iter(lambda: tuple(islice(arr_range, arr_size)), ()) list(chunk(range(30), 5)) |
Output:
[(0, 1, 2, 3, 4), (5, 6, 7, 8, 9), (10, 11, 12, 13, 14), (15, 16, 17, 18, 19), (20, 21, 22, 23, 24), (25, 26, 27, 28, 29)]
Method 6: Collections
One approach to splitting a list into chunks of size N without using a loop is to use the collections module. The collections module has a deque class that allows you to easily split a list into chunks of a specific size.
Here’s an example of how you can use the deque class to split a list into chunks of size N:
Python3
from collections import deque def split_list(input_list, chunk_size): # Create a deque object from the input list deque_obj = deque(input_list) # While the deque object is not empty while deque_obj: # Pop chunk_size elements from the left side of the deque object # and append them to the chunk list chunk = [] for _ in range(chunk_size): if deque_obj: chunk.append(deque_obj.popleft()) # Yield the chunk yield chunkinput_list = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]chunk_size = 3chunks = list(split_list(input_list, chunk_size))print(chunks) # [[1, 2, 3], [4, 5, 6], [7, 8, 9], [10]] |
[[1, 2, 3], [4, 5, 6], [7, 8, 9], [10]]
The deque class allows you to easily remove elements from the left or right side of the list, making it easy to split the list into chunks of a specific size. The code uses a while loop and a generator function to iterate over the list and yield the chunks one at a time. The loop breaks when the deque is empty, which indicates that all elements have been processed.
This approach has a time complexity of O(n) and a space complexity of O(n), where n is the size of the input list.
Method 7: Partial assignment
Here’s an example of how you can easily process list by chunks of size N:
Python3
my_list = list(range(10))chunk_size = 3while my_list: chunk, my_list = my_list[:chunk_size], my_list[chunk_size:] print(chunk) |
[0, 1, 2] [3, 4, 5] [6, 7, 8] [9]
