Request for elucidation: enhanced generators

[Ant]

Ben Sizer wrote:
...
> But do you have an example of such a use case? That's what I'm missing
> here.

I've been looking at this myself, trying to understand the point of
coroutines. I believe that they boil down to generators which are able
to take in data as well as provide it. A simple way of looking at it
seems to be that a coroutine is a generator which can have its state
changed whilst it is still active. A silly example to illustrate:

# coroutine.py
def stateful_generator(people):
    greeting = "Hello"
    for person in people:
       received = (yield greeting + " " + person)
       if received:
           greeting = received

if __name__ == "__main__":
    people = ["bob", "henry", "jim-lad", "boney", "greebo", "badger"]
    gen = stateful_generator(people)

    print gen.next()                     # Hello bob
    print gen.next()                     # Hello henry
    print gen.send("Yo! ")            # Yo!  jim-lad
    print gen.next()                     # Yo!  boney
    print gen.send("Meow ")        # Meow  greebo
    print gen.next()                     # Meow  badger

So you can change the behaviour of the coroutine whilst it is running.
That's as far as I have got with them though - there are presumably
many other uses of coroutines out there as I guess this use case could
be simulated using generators and globals.