How to iterate over a list in chunks in python

How to iterate over a list in chunks in python

You can iterate over a list in chunks in Python by creating slices of the list and then iterating through those slices. This allows you to process the list in smaller, more manageable pieces. Here's a common way to do it:

def chunked_iterable(iterable, chunk_size): for i in range(0, len(iterable), chunk_size): yield iterable[i:i + chunk_size] # Example usage: my_list = [1, 2, 3, 4, 5, 6, 7, 8, 9] chunk_size = 3 for chunk in chunked_iterable(my_list, chunk_size): print(chunk)

In this code:

  1. chunked_iterable is a generator function that takes an iterable (iterable) and a chunk size (chunk_size) as arguments.

  2. Inside the function, a for loop iterates through the iterable in steps of chunk_size, creating slices of the original iterable using slicing notation iterable[i:i + chunk_size].

  3. The yield statement yields each chunk as it's generated, effectively creating an iterator that can be used in a for loop.

  4. In the example usage, a list my_list is defined, and a chunk size of 3 is specified. The for loop then iterates over the chunks of the list, printing each chunk.

You can adjust the chunk_size to control the size of the chunks as needed for your specific use case. This approach is useful when you have a large list and want to process it in smaller, more manageable portions to avoid memory issues or for parallel processing.

Examples

  1. Python iterate list in chunks using for loop:

    • Description: Learn how to iterate over a list in fixed-size chunks using a simple for loop.
    def iterate_chunks(lst, chunk_size): for i in range(0, len(lst), chunk_size): yield lst[i:i + chunk_size] my_list = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] chunk_size = 3 for chunk in iterate_chunks(my_list, chunk_size): print(chunk)

  2. Using itertools.islice to iterate list in chunks:

    • Description: Utilize itertools.islice to create an iterator slicing the list into chunks.
    from itertools import islice def iterate_chunks(lst, chunk_size): it = iter(lst) while True: chunk = list(islice(it, chunk_size)) if not chunk: return yield chunk my_list = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] chunk_size = 3 for chunk in iterate_chunks(my_list, chunk_size): print(chunk)

  3. Python chunked list iteration using numpy:

    • Description: Use NumPy to split a list into equal-sized chunks for iteration.
    import numpy as np def iterate_chunks(lst, chunk_size): return np.array_split(lst, len(lst) / chunk_size) my_list = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] chunk_size = 3 for chunk in iterate_chunks(my_list, chunk_size): print(chunk)

  4. Iterating over list in chunks with list comprehension:

    • Description: Employ list comprehension to split a list into chunks for iteration.
    def iterate_chunks(lst, chunk_size): return [lst[i:i + chunk_size] for i in range(0, len(lst), chunk_size)] my_list = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] chunk_size = 3 for chunk in iterate_chunks(my_list, chunk_size): print(chunk)

  5. Chunked list iteration using iter() and lambda function:

    • Description: Use iter() and a lambda function to create a chunked list iterator.
    def iterate_chunks(lst, chunk_size): it = iter(lst) chunk = list(lambda: list(islice(it, chunk_size)), []) while chunk: yield chunk my_list = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] chunk_size = 3 for chunk in iterate_chunks(my_list, chunk_size): print(chunk)

  6. Iterating list in chunks with while loop:

    • Description: Implement chunked list iteration using a while loop and list slicing.
    def iterate_chunks(lst, chunk_size): i = 0 while i < len(lst): yield lst[i:i + chunk_size] i += chunk_size my_list = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] chunk_size = 3 for chunk in iterate_chunks(my_list, chunk_size): print(chunk)

  7. Python chunked list iteration with itertools.groupby:

    • Description: Use itertools.groupby to iterate over a list in chunks.
    from itertools import groupby def iterate_chunks(lst, chunk_size): for i in range(0, len(lst), chunk_size): yield lst[i:i + chunk_size] my_list = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] chunk_size = 3 for chunk in iterate_chunks(my_list, chunk_size): print(chunk)

  8. Chunked list iteration with more_itertools.chunked:

    • Description: Utilize the more_itertools.chunked function to iterate over a list in chunks.
    from more_itertools import chunked my_list = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] chunk_size = 3 for chunk in chunked(my_list, chunk_size): print(chunk)

  9. Python iterate list in chunks using recursion:

    • Description: Implement a recursive approach to iterate over a list in chunks.
    def iterate_chunks(lst, chunk_size): if not lst: return yield lst[:chunk_size] yield from iterate_chunks(lst[chunk_size:], chunk_size) my_list = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] chunk_size = 3 for chunk in iterate_chunks(my_list, chunk_size): print(chunk)

  10. Chunked list iteration with zip_longest:

    • Description: Use zip_longest from itertools to iterate over a list in chunks, padding with a specified value if needed.
    from itertools import zip_longest def iterate_chunks(lst, chunk_size, fillvalue=None): args = [iter(lst)] * chunk_size return zip_longest(*args, fillvalue=fillvalue) my_list = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] chunk_size = 3 for chunk in iterate_chunks(my_list, chunk_size): print(list(chunk))

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