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Thread: QThread to run one or more QProcess

  1. 27th September 2011, 20:39 #1
    smhall316
    smhall316 is offline Beginner
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    Default Re: QThread to run one or more QProcess

    I am having some problems with running one or more QProcess's in a single QThread. My goal is to run one process at a time in a single thread, one after another. I am able to successfully do that but as these process's run I am noticing that my memory for the python GUI just starts consuming all of the memory over time. I made basic little command line programs which simply iterate to a value to simulate a long running program.

    When I start a process I wait for it to end using waitForFinished(-1). I assume since this is being done in a thread it should not affect my core Python GUI. Am I not using the QProcess within a QThread correctly? If I take out the waitForFinished(-1) then I always get an error that the thread was destroyed before it had completed. I am attaching the Python code below

    Thanks In Advanced!!

    Qt Code: 
    1. #!/usr/bin/env python
    2. '''
    3. Try making a responsive gui with programs running in the background
    4. '''
    5.  
    6. # Python modules
    7. import sys
    8.  
    9. # PyQt4 Modules
    10. from PyQt4.QtCore import *
    11. from PyQt4.QtGui  import *
    12.  
    13. class ThreadTest(QDialog):
    14.  
    15.     def __init__(self, parent=None):
    16.         super(ThreadTest, self).__init__(parent)
    17.  
    18.         self.setMinimumWidth(400)
    19.         self.setMinimumHeight(400)
    20.         self.setWindowTitle("Thread Test")
    21.  
    22.         self.thread    = IndividualThread()
    23.  
    24.         self.pbar   = QProgressBar()
    25.         self.label  = QLabel("")
    26.         self.p1Btn  = QPushButton("Run Program 1")
    27.         self.p2Btn  = QPushButton("Run Program 2")
    28.         self.p3Btn  = QPushButton("Run Program 3")
    29.  
    30.         self.pbar.setOrientation(Qt.Horizontal)
    31.         self.pbar.setRange(0,100)
    32.         self.pbar.setValue(0)
    33.         self.pbar.setInvertedAppearance(False)
    34.         self.pbar.setTextVisible(False)
    35.  
    36.         box = QVBoxLayout()
    37.         box.addWidget(self.p1Btn)
    38.         box.addWidget(self.p2Btn)
    39.         box.addWidget(self.p3Btn)
    40.         box.addWidget(self.label, 0, Qt.AlignCenter)
    41.         box.addWidget(self.pbar)
    42.  
    43.         self.setLayout(box)
    44.  
    45.         self.timer = QTimer()
    46.  
    47.         self.connect(self.p1Btn , SIGNAL('pressed()'), self.runP1)
    48.         self.connect(self.p2Btn , SIGNAL('pressed()'), self.runP2)
    49.         self.connect(self.p3Btn , SIGNAL('pressed()'), self.runP3)
    50.  
    51.         self.connect(self.timer     , SIGNAL('timeout()') , self.onTimeout)        
    52.         self.connect(self.thread    , SIGNAL('started()') , self.onThreadStarted)
    53.         self.connect(self.thread    , SIGNAL('finished()'), self.onThreadFinished)        
    54.  
    55.         self.connect(self.dsn_thread, SIGNAL('threadInfo'), self.onThreadInfo)
    56.  
    57.     def enableButtons(self, enable):
    58.         self.p1Btn.setEnabled(enable)
    59.         self.p2Btn.setEnabled(enable)
    60.         self.p3Btn.setEnabled(enable)
    61.         self.dsnBtn.setEnabled(enable)
    62.  
    63.     def runP1(self):
    64.  
    65.         self.label.setText("Running program 1")
    66.         self.thread.setCommand("/home/hall000s/python/threads/prog1_lnx")
    67.         self.thread.start()
    68.  
    69.     def runP2(self):
    70.         self.label.setText("Running program 2")
    71.         self.thread.setCommand("/home/hall000s/python/threads/prog2_lnx")
    72.         self.thread.start()
    73.  
    74.     def runP3(self):
    75.         self.label.setText("Running program 3")
    76.         self.thread.setCommand("/home/hall000s/python/threads/prog3_lnx")
    77.         self.thread.start()
    78.  
    79.     def onThreadInfo(self, msg):
    80.         self.label.setText(msg)
    81.  
    82.     def onTimeout(self):
    83.         # Update the progress bar
    84.         value = self.pbar.value()
    85.  
    86.         # Going forward or backwards?
    87.         if self.pbar.invertedAppearance():
    88.             if value-2 < self.pbar.minimum():
    89.                 self.pbar.setValue(self.pbar.minimum())
    90.                 self.pbar.setInvertedAppearance(False)
    91.             else:
    92.                 self.pbar.setValue(value-2)
    93.         else:
    94.             if value+2 > self.pbar.maximum():
    95.                 self.pbar.setValue(self.pbar.maximum())
    96.                 self.pbar.setInvertedAppearance(True)
    97.             else:
    98.                 self.pbar.setValue(value+2)
    99.  
    100.     def onThreadStarted(self):
    101.         print "Thread has been started"
    102.         self.timer.start(10)
    103.         self.enableButtons(False)
    104.  
    105.     def onThreadFinished(self):
    106.         print "Thread has finished"
    107.         self.timer.stop()
    108.         self.enableButtons(True)
    109.         self.pbar.setValue(0)
    110.         self.label.setText("")
    111.  
    112. class IndividualThread(QThread):
    113.  
    114.     def __init__(self, parent=None):
    115.         super(IndividualThread, self).__init__(parent)
    116.  
    117.         self.args = ""
    118.         self.command = ""
    119.  
    120.     def setArguments(self, arguments):
    121.         self.args = arguments
    122.  
    123.     def setCommand(self, command):
    124.         self.command = command
    125.  
    126.     def run(self):
    127.         process = QProcess()
    128.         process.start(self.command, self.args)
    129.         process.waitForFinished(-1)       
    130.  
    131. #
    132. # MAIN
    133. #
    134. if __name__ == '__main__':
    135.  
    136.     # Order matters from here on.
    137.     app = QApplication(sys.argv)
    138.     form = ThreadTest()
    139.     form.show()
    140.     sys.exit(app.exec_())
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    Added after 1 33 minutes:


    Ignore this, I figured out the problem. I wasn't paying attention to the amount of data I was writing out to stderr and stdout in my silly program, which was causing the memory to increase as the program executed.
    Last edited by smhall316; 27th September 2011 at 20:39.
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