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Comprehensions & generators

List/dict/set comprehensions, generator expressions, and lazy iteration.

5 matches

Batch Rows in Chunks with a Generator in Python

Group a list of row dicts into fixed-size chunks using a generator that yields one slice per call.

from typing import Iterator, List


def batch_rows(rows: List[dict], batch_size: int) -> Iterator[List[dict]]:
    for i in range(0, len(rows), batch_size):
        yield rows[i:i + batch_size]


if __name__ == "__main__":
    sample_rows = [
        {"id": 1, "name": "Alice"},
        {"id": 2, "name": "Bob"},
      …

15 0 Open

Comprehensions & generators easy

Chunk an Iterable into Batches with a Generator in Python

Yield fixed-size batches from any iterable lazily using itertools.islice inside a generator function.

generators iterators itertools

Python

from itertools import islice

def chunked(iterable, size):
    iterator = iter(iterable)
    while True:
        batch = list(islice(iterator, size))
        if not batch:
            break
        yield batch

if __name__ == "__main__":
    data = range(10)
    for batch in chunked(data, 3):
        print(batch)

14 0 Open

Comprehensions & generators easy

How to Build a Sliding Window Generator in Python

Create a generator that yields fixed-size overlapping slices of a sequence, useful for efficient windowed iteration.

generators sliding-window iteration

Python

def sliding_window(sequence, size):
    for i in range(len(sequence) - size + 1):
        yield sequence[i:i + size]

if __name__ == "__main__":
    data = [1, 2, 3, 4, 5]
    n = 3
    for window in sliding_window(data, n):
        print(window)

12 0 Open

Comprehensions & generators easy

How to Slice a Generator with islice in Python

Use itertools.islice to take the first n items from any iterable without materializing the whole sequence into a list.

itertools islice generators

Python

from itertools import islice


def first_n(iterable, n):
    """Return the first n items from an iterable."""
    return list(islice(iterable, n))


if __name__ == "__main__":
    numbers = range(10, 100)  # large iterable
    result = first_n(numbers, 5)
    print(result)  # [10, 11, 12, 13, 14]

14 0 Open

Comprehensions & generators easy

Take n items from an infinite Python generator

Uses itertools.islice to lazily take exactly n items from an infinite generator without exhausting it.

generators itertools islice

Python

from itertools import islice

def count_up_from(start=0):
    n = start
    while True:
        yield n
        n += 1

def take_n(generator, count):
    return list(islice(generator, count))

if __name__ == "__main__":
    gen = count_up_from(10)
    result = take_n(gen, 5)
    print(result)

11 0 Open

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