On 09:52 am, ser...@gmail.com wrote: >My target is just to deny request duplications. > >Reg. inlineCallbacks.. What do you think is it possible to implement >inlineCallbacks generator in the way allows multiple yields? (but do >not >modify Defferred)
No, this isn't possible. Single-use is a fundamental aspect of Deferred. Instead, you can make a second (and third, etc) Deferred that has the same result as the first. Jean-Paul > > >From: Laurens Van Houtven [mailto:_...@lvh.cc] >Sent: Monday, January 28, 2013 1:43 PM >To: ser...@gmail.com >Subject: Re: [Twisted-Python] inlineCallbacks: multiple yielding same >Defferred behaviour > > > >The short answer is that those models don't support chaining the way >Deferreds do, IIUC. > >I think a very similar thing was a bonus question at the tutorial >Stephen >Thorne and I gave at EuroPython last year. Do you want to cache results >as >well, or only not make duplicate requests when one is in-flight? > > > >On Mon, Jan 28, 2013 at 10:36 AM, Sergey V. Gerasimov ><ser...@gmail.com> >wrote: > >Hi Laurens, > > > >Thanks for your reply! > > > >I need something like this. > >A server that processes requests and handles situation when there are 2 >requests with same key. > > > >class Server(object): > > def __init__(self): > > self.requestsInProgress = {} # dict: key >-> >Deferred with result > > > > @defer.inlineCallbacks > > def request(self, key): > > in_progress = key in self.requests > > if in_progress: > > d = >self.requestsInProgress >[key] > > result = yield d > > else: > > d = process_request(key) > > self.requests[key] = d > > result = yield d > > del >self.requestsInProgress >[key] > > defer.returnValue(result) > > > >How can I implement the logic correctly? > > > >In my opinion it's very simple and clear concept to consider Deferred >just >like deferred execution of some action. In this case you should be able >to >get it's result (doing yield) many times (why not?). > > > > > >I have deal with Task-based programming and async functions (mechanism >similar to Deferred and inlineCallbacks decorated functions in Twisted) >in >Microsoft .NET. > >MS people have implemented Task (analogue of Deferred) in the way I >described. > > > > > > > >From: Laurens Van Houtven [mailto:_...@lvh.cc] >Sent: Monday, January 28, 2013 12:47 PM >To: ser...@gmail.com; Twisted general discussion >Subject: Re: [Twisted-Python] inlineCallbacks: multiple yielding same >Defferred behaviour > > > >I'm not entirely sure why you feel this is unintuitive or why you >should >need a workaround; in any other case, deferreds work pretty much the >same >way. > >When reading this code, the first question that pops up in my head is: >why >are you doing this instead of just using the result that you already >have >(and assigned to a name)? How did this waiting-twice-on-one-deferred >happen? > > > >On Mon, Jan 28, 2013 at 8:47 AM, Sergey V. Gerasimov <ser...@gmail.com> >wrote: > >It's not intuitively clear why multiple yielding the same Defferred in >function decorated with defer.inlineCallbacks get different results: > > > >@defer.inlineCallbacks > >def f(): > > d = defer.succeed(1) > > result = yield d > >print result > > result = yield d > >print result > > > >Output: > >1 > >None > > > >Probably we SHOULD NOT think if "d" was or was not yielded before when >using >inlineCallbacks.. > > > >Are they some workarounds? > > > > >_______________________________________________ >Twisted-Python mailing list >Twisted-Python@twistedmatrix.com >http://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python > > > > >-- > >cheers > >lvh > > > > >-- > >cheers > >lvh _______________________________________________ Twisted-Python mailing list Twisted-Python@twistedmatrix.com http://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python
