Coroutine helpers and example

coroutine_helper.py

def coroutine(func):
    def start(*args, **kwargs):
        cr = func(*args, **kwargs)
        next(cr)
        return cr
    return start


@coroutine
def broadcast(*sinks):
    try:
        while True:
            item = yield
            for sink in sinks:
                sink.send(item)
    finally:
        for sink in sinks:
            sink.close()


def send_all(source, sink):
    try:
        for item in source:
            sink.send(item)
    finally:
        sink.close()

example.py

@coroutine
def plus1(sink):
    """Adds 1 from the source and sends it to `sink`."""
    try:
        while True:
            n = yield
            sink.send(n + 1)
    finally:
        sink.close()


@coroutine
def printer():
    while True:
        n = yield
        print(n)


def main():
    values = [1, 2, 3]
    sink = broadcast(
        printer(),
        plus1(printer()),
    )
    send_all(values, sink)


main()