Can you post a full example on pastsbin or gist? It sounds like something
is happening before the event loop.
Also for subprocess, you should pass the command as a list so you don't
need shell=True

command=["avconv", "-i", self.inputFile, "-b",
self.bitRatesList[self.bitRate.currentIndex()], "-s",
self.sizeList[self.sizeSel.cur rentIndex()], self.outputFile]

Generally though, I think the QProcess approach is more robust as it plays
nicely with the event loop.

With the qtimer then reason I was using it plus a 100 ms timeout was to
have the callback placed into the event loop and run after the app had
fully started and signals would work. In a real case, the process would
probably get started by some action in your running app. Like a button
press or a response to some signal.
 On Mar 18, 2013 11:00 PM, "Ricardo Viana" <[email protected]> wrote:

> Thank you very much for the help Justin.
>
> i followed your code on gist.
>
> here is what i have now:
>
> -----code----
>
>
>     def timer(self):
>         QtCore.QTimer.singleShot(100,**self.export)
>
>
>
>     def export(self):
>         self.log.append("started")
>
>         self.proc=subprocess.Popen("**avconv -i %s -b %s -s %s %s"
> %(self.inputFile,self.**bitRatesList[self.bitRate.**currentIndex()],
> self.sizeList[self.sizeSel.**currentIndex()],self.**
> outputFile),shell=True,stdout=**subprocess.PIPE)
>         while True:
>             output=self.proc.stdout.**readline()
>             if not output:
>                 break
>             QtGui.qApp.processEvents()
>             self.log.append(output.strip()**)
>
>
>
>
> -----code----
>
>
> what is happening is the following. The self.log.append("started") only
> shows when the subprocess terminates and it should be the
> other way around. Also i can't append the output.strip to the
> QTextBrowser(self.log) i have. it shows nicely on the terminal but not in
> the GUI.
>
> Another thing i can't figure is why i have to say to subprocess ->
> Shell=True. In your code you don't have it. but if i run it that way
> i get an error :
>
> File "/usr/lib/python2.7/**subprocess.py", line 1249, in _execute_child
>     raise child_exception
> OSError: [Errno 2] No such file or directory
>
>
>
>
>
>
> On 03/16/2013 03:29 AM, Justin Israel wrote:
>
>> QProcess has signals that indicate when new data is ready to read from
>> your process, allowing to to get line updates. Also, in your example, you
>> are going to be blocking the event loop with your for loop.
>>
>> I put together an example of each of those for you here:
>> https://gist.github.com/**justinfx/5174795<https://gist.github.com/justinfx/5174795>
>>
>> The first example shows how to monitor the QProcess for new output
>>
>> The second shows how to use subprocess in a way that you can loop over
>> the output, but still pump the event loop. If your lines are being emitted
>> quickly you probably don't need to make the call for every loop, but rather
>> you could call on on every 10 lines...or 100 lines.. or whatever is
>> appropriate to give your main gui thread a chance to process the pending
>> events:
>>
>> i.e.
>>
>> i = 0
>> while True:
>>      line = process.stdout.readline()
>>      if not line:
>>          break
>>
>>      # process line
>>
>>      # process event loop every 10 lines
>>      if i % 10 == 0:
>>          QtGui.qApp.processEvents()
>>      i +=1
>>
>>
>> -- justin
>>
>>
>>
>> On Thursday, March 7, 2013 5:22:19 AM UTC+13, olheiros wrote:
>>
>>> Hi Fellas!
>>>
>>>
>>>
>>> i'm trying to build my own video converter gui on a Linux. Using Pyqt4.
>>>
>>> I'm using avconv command line converter.
>>>
>>>
>>>
>>> I have setup all parameters and it is working fine.
>>>
>>>
>>>
>>> The thing is i would like to have some kind of progress feedback.
>>>
>>> Does anyone know how to retrieve the command line feedback so
>>>
>>> i can hook it to some kind of expression to drive the QProgressBar?
>>>
>>>
>>>
>>> thank you very much
>>>
>>>
>>>
>>> --
>>>
>>> //////////////////////////////**//////
>>>
>>> Ricardo Viana
>>>
>>> VFX Generalist
>>>
>>
>
> --
> //////////////////////////////**//////
> Ricardo Viana
> VFX Generalist
>
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