[PySide] Signal emitted on a worker thread not being received by main thread

[Algis Kabaila]

William,

It may bee worth while to read about QTimer [QtCore]( Mark Summerfield's 
"Rapid GUI Porgramming with Python and Qt", pp. 373, 376. Also QTime 
[QtCore] and 
[QTimeEdit [QTGui] p 576.  I vaguely recall that there was discussion why 
he used QTimer of Qt library rather than the simpler "sleep" of Python.
Just a shot in the dark - it might be just what is needed.  Worth a try, I 
think. 

Al.


On Monday 08 April 2013 23:32:45 William Dias wrote:

Lucas,


Yes, I could, but the question is: why this is not working properly with 
qt libraries only? Why the slot is not being called? The weird thing is 
that the issue just occurs occasionally. In the last battery of tests I 
ran, I've got 149 threads created and only 2 of them didn't make the call 
to the slot. 




2013/4/8 Lucas Tanure <ltanure at gmail.com>

Could you use the queue in python ? with Queue.get([block[, timeout]]) ? 


Lucas A. Tanure Alves
+55 (19) 88176559



On Mon, Apr 8, 2013 at 6:59 PM, William Dias <william.dias at gmail.com> 
wrote:

Hi, Tibold. Thanks for your reply.


If I first move my worker to the new thread and then make the connection 
should it work?


According to the documentation, it would use an auto-connection and since 
emitter and receiver don't have the same thread affinity, it would create 
a queued connection. Is it right? 


Best,



2013/4/8 Tibold Kandrai <kandraitibold at gmail.com>

Hi,
 
I think you’ll have to use queued connection when you connect the 
photoStatus signal to the photoStatus slot. 
 
See: 
http://qt-project.org/doc/qt-4.8/threads-qobject.html#signals-and-slots-
across-threads 
 
Cheers,
Tibold
  
From: pyside-bounces+kandraitibold=gmail.com at qt-project.org 
[mailto:pyside-bounces+kandraitibold=gmail.com at qt-project.org] On Behalf 
Of William Dias
Sent: 2013 April 08, Monday 17:01
To: pyside at qt-project.org
Subject: [PySide] Signal emitted on a worker thread not being received by 
main thread 
 
Hi,
 
I am facing an intermittent problem with my PySide application. I have a 
GUI that spawns several threads that are responsible for sending photos to 
a web server. The threads are created as shown bellow: 
 
photoConnectionThread = QThread()
photoConnectionObject = http_connection.PhotoConnection(self.filename) 
photoConnectionObject.photoStatus.connect(self.photoStatus)             
photoConnectionObject.moveToThread(photoConnectionThread) 
photoConnectionThread.started.connect(photoConnectionObject.work)
photoConnectionThread.finished.connect(self.threadFinished) 
photoConnectionThread.start()
 
My worker thread tries to upload a photo only once and then emits a signal 
to the main thread so that the status can be updated in a database.  
 
def work(self):
                        logger.info("photo object created on thread " + 
str(self.thread())) 
                        status = sendPhoto(self.filename)
                        self.photoStatus.emit(self.filename, status) 
                        QThread.sleep(5)
                        logger.info("exiting thread " + 
str(self.thread())) 
                        self.thread().exit(0)
 
The problem is that, sporadically, the main thread does not receive the 
signal and consequently doesn't get the status updated. 
 
Does anybody have any idea why this is happening?
 
I am using:
Python 2.7
PySide 1.1.1
Windows 7 
 
Thank you!




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