Coroutines in Python

producer_consumer.py

"""Producer/Consumer coroutines."""

import asyncio

q = asyncio.Queue(7)

def reader(iterable):
    """Producer."""
    it = iter(iterable)
    while True:
        while not q.full():
            # Create a new item
            try:
                value = next(it)
                print(".")
            except Exception as e:
                value = e
            # Add it to the queue
            q.put_nowait(value)
        # Yield to consumer
        yield printer


def printer():
    """Consumer."""
    while True:
        while not q.empty():
            # Remove item from the queue
            value = q.get_nowait()
            if isinstance(value, Exception):
                raise value
            # Use item
            print(value)
        # Yield to producer
        yield reader


if __name__ == "__main__":
    d = dict()
    d[reader] = reader(range(100))
    d[printer] = printer()
    current = reader
    while True:
        try:
            current = next(d[current])
        except StopIteration:
            break