[PyQt] Long running processes, threads, progress dialog

Catriona Johnson catriona.johnson at gmail.com
Thu Mar 24 01:00:03 GMT 2011

>> Hello
>> I have a GUI application that occasionally has a number of long
>> running processes - eg data deletions , html report generation.
>> I have a custom progress widget that displays a spinning icon (my
>> client didn't like the Qt QProgressDialog) which I display during
>>long running processes - the user doesn't need to be able to interact
>> with the GUI while this is happening.
>> I have started to implement a worker thread to perform these long
>> running processes. My question is do I initiate each process from the
>> Thread's run method as follows or does each operation have its own
>> thread ?? Do I need to use a secondary thread at all? Is there a
>> better way ??
>> def run(self):
>>               if self.operation == A_DELETE:
>>                       self.completed = AModel.model().removeRecord(self.identity)
>>               elif self.operation == B_DELETE:
>>                       self.completed = BModel.model().removeRecord(self.identity)
>>               elif self.operation == REPORTS:
>>                       self.completed = ReportWriter.generateReport()
>>               self.stop()
>>               self.emit(SIGNAL("finished(bool)"), self.completed)
>>               self.wait()

>You may want to read this article, which is mostly valid also for PyQt:
>       http://www.linuxjournal.com/article/9602
>From a PyQt POV and depending on where the action is, the presence of
>the GIL might want to be taken into account..

Thanks for that Pete - it is a good article.

My case is not that complicated though. I am reading and sometimes
updating binary files that contain the data for the application. These
processes are never concurrent and do not connect to a database. My
understanding is from the article that each process has a thread and
the process is run from the thread's run method?

Implementing threading does seem a little bit of overkill if all I
want is a modal progress dialog to display while the operation is
occurring. What is the best way to do it.

I did try a QProgressDialog as follows but although it was displayed
there was no animation. I want an indeterminate progress bar

progressDialog = QProgressDialog()
progressDialog.setValue(-1) # As set in Designer



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