2017-01-18 20:11 GMT+01:00 Elvis Stansvik <elvst...@gmail.com>: > 2017-01-18 20:04 GMT+01:00 Elvis Stansvik <elvst...@gmail.com>: >> 2017-01-18 8:17 GMT+01:00 Frank Rueter | OHUfx <fr...@ohufx.com>: >>> Hi Thiago, >>> >>> thanks for your quick reply. I will try and give some more context: >>> I use the python requests module inside my PySide app to post requests to a >>> website. Some of those requests return a lot of data that I need to parse to >>> be able to show progress, other requests are file downloads that I need >>> progress bars for as they stream onto disk. >>> I had tried to not use threads and use QApplication.processEvents() for each >>> data chunk downloaded, but that made the download about 4-5 times slower. >>> Introducing threading made a huge difference. >> >> Right, you won't get a good result with that approach. It's always >> good to be up front with any special circumstances like this (using a >> networking API that does not run on top of the Qt event loop). >> >>> >>> My app can download a list of files at the same time. Depending on the >>> situation and the user request, the list of files to be downloaded can >>> happen asynchronously, in other situations they need to be downloaded one >>> after the other. >> >> I think this is what confused Thiago: What you mean is sequential (as >> opposed to parallell), not synchronous. >> >> If you have one QThread that depends on the completion of another, >> then no, I don't think there's a convenient API in Qt to express that >> relationship and run the threads infrom sequence. You'll have to string >> them together yourself, or maybe use something else like Threadweaver. >> I could be wrong of course :) > > Another approach is of course to ditch the threading and use the > asyncronous QNetworkAccessManager from Qt, instead of using the Python > requests module. You can use the downloadProgress/uploadProgress of
downloadProgress/uploadProgress *signals*. > the QNetworkReply you get from get(..) or post(..) if you want to show > progress (haven't used it myself). > > Elvis > >> >> Elvis >> >>> >>>>>All I can tell you is that you don't need to do what you're trying to do, >>>>> since you don't need threads in the first place. >>> If I can avoid threads to do the above I would be more than happy to adjust >>> and get rid of them again, but I haven't managed to find a non-threaded >>> approach that doesn't slow down the download significantly. >>> >>> Cheers, >>> frank >>> >>> >>> On 18/01/17 6:26 PM, Thiago Macieira wrote: >>>> >>>> On quarta-feira, 18 de janeiro de 2017 17:21:46 PST Frank Rueter | OHUfx >>>> wrote: >>>>> >>>>> Hi, >>>>> >>>>> I got another threading question for the pros out there: >>>>> >>>>> In my current application I am using QThread objects and >>>>> QObject.moveToThread() to enable my GUI to download multiple files while >>>>> updating progress bars in the main event loop. This is the respective >>>> >>>> As usual, the usual disclaimer: you do not need threads to do networking >>>> or >>>> file I/O. The combined overhead of the networking I/O and saving of the >>>> files is >>>> unlikely to overwhelm the event loop to the point that the progress bar >>>> can't >>>> update smoothly. >>>> >>>> I'm not saying impossible, but it's unlikely. >>>> >>>>> snippet of code: >>>>> self.worker = MyClass() >>>>> self.workerThread = QtCore.QThread() >>>>> self.worker.moveToThread(self.workerThread) >>>>> >>>>> The trouble is when the user wants to download multiple files at once. >>>>> In my current implementation that all works fine and I see multiple >>>>> progress bars do there thing. >>>>> However, there are cases when I need to force the download threads to be >>>>> synchronous. I had hoped that I can use QThreadPool with QThreads, but >>>>> turns out I need QRunnables in this case, and those don't have the same >>>>> signals as QThread. >>>> >>>> Why do you need to force them to be synchronous? And synchronous with >>>> what? >>>> With each other? Or do you mean sync() in the file saving? >>>> >>>> Finally, what does being synchronous have to do with signals? >>>> >>>>> So my question is: >>>>> Is there a good way to use QThreads in a queue which is controlled by >>>>> the main thread, or should I re-write my code and subclass QRunnable to >>>>> add the signals I need (i.e. the ones that QThread has by default)? >>>> >>>> The whole point of QThread is that the code it runs is independent of >>>> anything >>>> else. Only the OS scheduler decides when it's time to run it or suspend >>>> it. >>>> >>>>> In the latter case I guess I'd have to inherit from both QObject and >>>>> QRunnable, is this ok? >>>> >>>> Right. >>>> >>>> But we still don't understand what you're trying to do. All I can tell you >>>> is >>>> that you don't need to do what you're trying to do, since you don't need >>>> threads in the first place. >>>> >>> >>> _______________________________________________ >>> Interest mailing list >>> Interest@qt-project.org >>> http://lists.qt-project.org/mailman/listinfo/interest _______________________________________________ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
