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?