QThread with Python Popen freezing on sizable external program

[jkrienert]

As it stands, a QThread worker class enables the external call of an *.exe with Popen. While this external process is running, a QProgressBar within the governing class needs to be periodically updated.

The sample below works for a few percentage increments, then it suddenly freezes until the process is complete.

class workerThread(QThread):
    progress = pyqtSignal(int)
 
    def runProgram(self,directory):
       file = directory+'fileName.txt'
       program = sys.path[4] + "/Root/GIS_Pre_Processor.exe"
       runProgram = Popen([program,file],shell=True,cwd=directory)
       currentProgress = 45
       while runProgram.poll() is None:
           time.sleep(1.5)               #<=== makes it through a couple of these loops
           currentProgress = currentProgress + 5
           self.progress.emit(currentProgress)
       self.progress.emit(100)

class workerThread(QThread):
    progress = pyqtSignal(int)

    def runProgram(self,directory):
       file = directory+'fileName.txt'
       program = sys.path[4] + "/Root/GIS_Pre_Processor.exe"
       runProgram = Popen([program,file],shell=True,cwd=directory)
       currentProgress = 45
       while runProgram.poll() is None:
           time.sleep(1.5)               #<=== makes it through a couple of these loops
           currentProgress = currentProgress + 5
           self.progress.emit(currentProgress)
       self.progress.emit(100)

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Does this suggest an improper implementation of QThread?

[wysota]

What is the reason for the while loop? Why don't you use a timer or QTimeLine? And QProcess for handling the worker process.

[jkrienert]

I had not yet investigated QProcess, but currently I am having trouble implementing it to any functioning result.

fileName = someDirectory+'anInterestingFile.txt'
Program = sys.path[4] + "/someDirectory/console.exe"
runTheProgram = QProcess()
runTheProgram.setWorkingDirectory(outsideDirectory)
runTheProgram.finished.connect(self.parseResults)
runTheProgram.execute(Program,fileName)

fileName = someDirectory+'anInterestingFile.txt'
Program = sys.path[4] + "/someDirectory/console.exe"
runTheProgram = QProcess()
runTheProgram.setWorkingDirectory(outsideDirectory)
runTheProgram.finished.connect(self.parseResults)
runTheProgram.execute(Program,fileName)

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Where 'fileName' is the first and only argument to be entered into the console 'Program'.
The program itself closes automatically wether successful or not, but I would like to somehow check for assurance that it indeed has
ran and executed the singular argument 'fileName' sent.

Currently it closes without executing the 'fileName' argument.

[jkrienert]

The implementation of QProcess must be off-tilt, as with the following example, the Ui hangs just as with the initial postings use of POpen...
Granted, the program does run - but eventually crashes in the process (after ~20 sec.) without any progressBar updates sent where as with the identical 'NAMfile' command used with POpen
results in success.

NAMfile = str(self.modDirectory)+'mfnam.txt'
        MODFLOW = sys.path[4] + "/GraphicGroundwater/mf2005.exe"
 
        qMODFLOW = QProcess()
        qMODFLOW.setWorkingDirectory(self.modDirectory)
        qMODFLOW.finished.connect(self.returnResultStats)
        qMODFLOW.start(MODFLOW,[r"%s"%(NAMfile)])
 
        qMODFLOW.waitForFinished()
        while not qMODFLOW.ExitStatus():
            time.sleep(0.5)
            currentProgress = currentProgress + 2
            self.progress.emit(currentProgress)

NAMfile = str(self.modDirectory)+'mfnam.txt'
        MODFLOW = sys.path[4] + "/GraphicGroundwater/mf2005.exe"

        qMODFLOW = QProcess()
        qMODFLOW.setWorkingDirectory(self.modDirectory)
        qMODFLOW.finished.connect(self.returnResultStats)
        qMODFLOW.start(MODFLOW,[r"%s"%(NAMfile)])

        qMODFLOW.waitForFinished()
        while not qMODFLOW.ExitStatus():
            time.sleep(0.5)
            currentProgress = currentProgress + 2
            self.progress.emit(currentProgress)

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[jefftee]

I'm not entirely sure I understand what you're doing, but a couple of observations:

- QProcess:waitForFinished() will block for 30,000 milliseconds (30 seconds). If your process ends before 30 seconds is up, it will return. It will also return after 30 seconds expires even if your QProcess is still running. Just used the QProcess signals to get state changes and/or finished notification, etc.

- Not sure what your while loop is trying to accomplish. You will get the process exit code and exit status in the finished signal. Use that to determine whether your process ran successfully.

- Your progress bar updates are likely not reflecting the completion status since you are arbitrarily updating your progress every .5 seconds. How many seconds will the process run to completion, does it vary?

- You can read output of your QProcess, so if it's outputing any information while running, you can consume that output to get a better completion status if your process normally displays this. I have used QProcess like this in the past where i read the stdout and stderr of the QProcess to determine progress, etc.

Good luck.