Most "active" coroutine library project?

Simon Forman sajmikins at
Fri Sep 25 21:25:32 CEST 2009

On Fri, Sep 25, 2009 at 2:07 PM, Jason Tackaberry <tack at> wrote:
> On Fri, 2009-09-25 at 15:42 +0000, Grant Edwards wrote:
>> You can't call a function that yields control back to the other
>> coroutine(s).  By jumping through some hoops you can get the
>> same effect, but it's not very intuitive and it sort of "feels
>> wrong" that the main routine has to know ahead of time when
>> calling a function whether that function might need to yield or
>> not.
> Not directly, but you can simulate this, or at least some pseudo form of
> it which is useful in practice.  I suppose you could call this "jumping
> through some hoops," but from the point of view of the coroutine, it can
> be done completely transparently, managed by the coroutine scheduler.
> In kaa, which I mentioned earlier, this might look like:
>        import kaa
>        @kaa.coroutine()
>        def task(name):
>           for i in range(10):
>              print name, i
>              yield kaa.NotFinished  # kind of like a time slice
>        @kaa.coroutine()
>        def fetch_google():
>           s = kaa.Socket()
>           try:
>              yield s.connect('')
>           except:
>              print 'Connection failed'
>              return
>           yield s.write('GET / HTTP/1.1\nHost:\n\n')
>           yield (yield
>        @kaa.coroutine()
>        def orchestrate():
>            task('apple')
>            task('banana')
>            page = yield fetch_google()
>            print 'Fetched %d bytes' % len(page)
>        orchestrate()
> The two task() coroutines spawned by orchestrate() continue to "run in
> the background" while any of the yields in fetch_google() are pending
> (waiting on some network resource).
> It's true that the yields in fetch_google() aren't yielding control
> _directly_ to one of the task() coroutines, but it _is_ doing so
> indirectly, via the coroutine scheduler, which runs inside the main
> loop.
> Cheers,
> Jason.

So Kaa is essentially implementing the trampoline function.

If I understand it correctly MyHDL does something similar (to
implement models of hardware components running concurrently.)

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