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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 easy

How to Lazily Transform Items in Python with a Generator

Map a transform function over an iterable lazily with a generator so items are processed on demand, not up front.

generators lazy evaluation mapping

Python

def lazy_map(items, transform):
    for item in items:
        yield transform(item)

def double(x):
    return x * 2

def upper(s):
    return s.upper()

if __name__ == "__main__":
    numbers = [1, 2, 3, 4, 5]
    doubled = lazy_map(numbers, double)
    print("Doubled numbers:", end=" ")
    for value in doubled:
  …

14 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

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