multiprocessing's imap() wrapper that lazily creates chunks

imap_lazy.py

from multiprocessing import Pool
from itertools import islice

def imap_lazy(func, iterable, pool_size=10, chunk_size=10000,
              maxtasksperchild=1000, unordered=False):
    p = Pool(processes=pool_size, maxtasksperchild=maxtasksperchild)

    while True:
        chunk = list(islice(iterable, chunk_size))
        if not chunk:
            break

        imap_func = p.imap_unordered if unordered else p.imap
        for ret in imap_func(func, chunk):
            yield ret

    p.terminate()