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Comprehensions & generators

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

3 matches

How to Generate Primes with a Generator in Python

Generate prime numbers up to a limit using the Sieve of Eratosthenes wrapped in a generator expression for lazy evaluation.

generators sieve primes

Python

def prime_generator(limit):
    sieve = [True] * (limit + 1)
    sieve[0] = sieve[1] = False

    for i in range(2, int(limit ** 0.5) + 1):
        if sieve[i]:
            for j in range(i * i, limit + 1, i):
                sieve[j] = False

    return (num for num, is_prime in enumerate(sieve) if is_prime)


if __n…

15 0 Open

Comprehensions & generators medium

How to filter a generator with a predicate function in Python

This code defines a generator function that yields only items from an iterable that satisfy a given predicate, then tests it with even and positive number filters.

generators filtering lazy evaluation

Python

def filter_gen(predicate, iterable):
    for item in iterable:
        if predicate(item):
            yield item

def is_even(num):
    return num % 2 == 0

def is_positive(num):
    return num > 0

if __name__ == "__main__":
    numbers = range(-5, 10)
    
    even_numbers = list(filter_gen(is_even, numbers))
    p…

10 0 Open

Comprehensions & generators medium

How to stream parse JSON arrays in Python

This code demonstrates two generators: one that streams a JSON array as individual chunks, and another that incrementally parses those chunks into Python objects using json.JSONDecoder.

json generator streaming

Python

import json


def json_array_stream(items):
    """Generator that yields JSON-encoded values one at a time."""
    yield "["
    for i, item in enumerate(items):
        if i > 0:
            yield ","
        yield json.dumps(item)
    yield "]"


def parse_json_stream(stream):
    """Consumes a stream of JSON fragme…

14 0 Open

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