Duncan Booth wrote: [ snip sections about why the single layer aspect can be helpful ]
> I'm happy with generators as they are: they're a great solution to a > problem that most of us didn't realise we had until the solution came > along. That doesn't mean that I wouldn't also like to have a separate > coroutine library, but I would use it to replace situations that might > otherwise have to use threads, not to replace generators. Oh agreed. For that, it would probably be nice to see greenlets (or something similar) make it into the standard library, but I suspect that's too much of a jump at the moment. I think for me, what we tend to do is prototype something as a stub program, and either turn that into a threaded component or a generator component. If I was to do something halfway I'd probably look at greenlets at the moment, though so far we've not found a use for that. (which is relatively suprising) Any time it's looked useful, generally it's actually meant "spin this control out to another smaller component". That's generally then resulted in that spun out component being reusable. For example, probable border case for coroutines is in this: http://kamaelia.svn.sourceforge.net/viewvc/kamaelia/branches/private_MPS_Scratch/Apps/Kamaelia-Grey/App/greylisting.py?revision=3684&view=markup We do do something that implies full coroutine support would be useful - specifically the calls: yield WaitComplete(self.getline(), tag="_getline1") ... yield WaitComplete(self.getline(), tag="getline2") To: 31 def getline(self): 32 control_message = "" 33 while 1: 34 while not self.anyReady(): 35 self.pause(); 36 yield 1 37 while self.dataReady("control"): 38 control_message = self.recv("control") 39 if isinstance(control_message, socketShutdown): 40 self.client_connected = False 41 if self.dataReady("inbox"): 42 self.logging_recv_connection() 43 return 44 else: 45 if not self.client_connected : 46 self.breakConnection = True 47 return 48 yield 1 (This is of course faking full co-routines by getting the caller to call something else temporarily) The thing is, if we split that out to an external component, there's potential benefits. *shrug* IMO, code should be written for clarity first, so simply being able to have this as pure co-routines may be useful. However, being able to tag the calls like this: yield WaitComplete(self.getline(), tag="_getline1") ... yield WaitComplete(self.getline(), tag="getline2") Meant that I could run an introspector: 506 Pipeline( 507 PeriodicWakeup(), 508 WakeableIntrospector(), 509 ).activate() And was able to see that some clients were misbehaving at different time points, but also seeing clearly able to see what state the component was waiting/hanging in when dealing with broken clients, and able to add in timeouts trivally. cf: *debug* 'THREADS'['Axon.Microprocess.microprocess_7068_getline1', 'Kamaelia.Chassis.Graphline.Graphline_7062', 'Kamaelia.Chassis.Pipeline.Pipeline_7', ... snip ... 'Kamaelia.Internet.ConnectedSocketAdapter.ConnectedSocketAdapter_7059', 'Kamaelia.Internet.Selector.Selector_11', 'Kamaelia.Internet.TimeOutCSA.ActivityMonitor_7060', 'Kamaelia.Internet.TimeOutCSA.ResettableSender_7061', '__main__.GreylistServer_8', '__main__.PeriodicWakeup_5', '__main__.TCPS_10', '__main__.WakeableIntrospector_6'] Now you could of course design a coroutine system for python to do that and I'd hope if anyone did, they'd think of it being useful to trace the where a co-routine is currently stuck :-) All that said, my personal primary aim for kamaelia is to try and make it into a general toolkit for making concurrency easy & natural (as well as efficient) to work with. If full blown coroutines turn out to be part of that c'est le vie :-) I think it's a bit like the arguments around lambda being limited to a single expresson vs a throwaway def. Both are useful, being stuck with one or the other is more limiting than is perhaps ideal. > Thanks you. I really do intend most of my posts to be helpful. Likewise :-) Have fun :-) Michael. -- http://mail.python.org/mailman/listinfo/python-list
