transducer.py

from itertools import imap, ifilter, islice, count

def xf(v):
    mapped = imap(lambda x: x * 2, v)
    return ifilter(lambda x: x % 3 == 0, mapped)

print(list(islice(xf(count()), 10)))


def partition_all(size, items):
    buf = []
    for item in items:
        buf.append(item)

        if len(buf) == size:
            yield buf
            buf = []
    if buf:
        yield buf

print(list(partition_all(3, range(50))))
print(list(islice(partition_all(3, count()), 5)))