PySide 6: GUI Freezing even when using QThreadPool class

ccortez

I am currently building a GUI using PySide6. I am running into some issues with the qthreadpool threading.

I have a method where I perform some heavy computation, that will end up freezing the GUI if left on the main thread. I have used qthreadpool for otber methods in my code, and it has worked just fine. For some reason, there is a specific part of my code right now that isn't working as intended. I launch that method in a threadpool thread, and the GUI still freezes up. To me this means that it's not making it outside the mainthread, or there is some other bigger issue. I can't really narrow it down, since I've been using qthreadpool this whole time and it has worked fine.

ANy guidance or help with this would be great, I am a bit stuck at this point.

Here is my code:

class dataSignal(QObject):
    data_received = Signal(object)
class DataPlotting(QMainWindow):
    def __init__(self):
        super(DataPlotting, self).__init__()
        # Styling and window layout
        screen = QApplication.primaryScreen().size().width()
        window = self.frameGeometry().width()
        self.move(int(screen / 2) - int(window / 2),0)
        self.setWindowTitle('GUI App')

        self.setStyleSheet('''...''')

        # Initializing Variables for data log file
        self.threadpool = QThreadPool()
        self.plotting_signal_con = dataSignal()
        self.plotting_signal_con.data_received.connect(self.plotting_ready)
        self.data = {}

        # Sample Button to Graph Data, this is the button where I launch heavy computation
        # but the GUI still freezes
        self.graph = QPushButton('Graph Data', self)
        self.graph.setToolTip('Graph Data')
        self.graph.setEnabled(False)
        self.graph.clicked.connect(self.threader) # connects to funciton that launches thread

    @Slot()
    def plotting_ready(self, info):
       # Here all i do is  call a function in another file that plots the data based on selected x and y 
       # variables (not included in this code)
        self.console.append(info)
        plotting(list(self.data.values()), self.xvar, self.yvars, self.footers)

    def plot_cb(self, info):
        self.plotting_signal_con.data_received.emit(info)

   # We launch the thread here 
    def threader(self):
        self.threadpool.start(self.ProcessDataLogs2(self.plot_cb))

    def ProcessDataLogs2(self, callback):
         for i, file in enumerate(self.data):
            #This is where the heavy computation happens 
            # All i really do is read in a file from pandas based on different conditions, so I am just going to  
            # include that line 
            df = pd.read_csv(file
            self.data[file]) = df
         
         # Once that is done, we send info in the call back function to signal that this process is done, 
         and it goes to the function plotting_ready
         info = 'Data Processing Finished & Plots Created...'
         callback(info)

SGaist

Hi,

I think the issue is that you are using a callback to emit the signal.

If you want to emit a signal from a different thread, you should use QMetaObject::invokeMethod.

ccortez

@SGaist Hi I appreciate your response.

I dont think that this is the problem if I am being honest. The reason why I say that is because I am doing the exact same process for another method in my code, and that one works exactly as intended.

If it helps, here is the code for that chunk:

class dataSignal(QObject):
    data_received = Signal(object)
class DataPlotting(QMainWindow):
    def __init__(self):
        super(DataPlotting, self).__init__()
        # Styling and window layout
        screen = QApplication.primaryScreen().size().width()
        window = self.frameGeometry().width()
        self.move(int(screen / 2) - int(window / 2),0)
        self.setWindowTitle('GUI App')

        self.setStyleSheet('''...''')

        # Initializing Variables for data log file
        self.threadpool = QThreadPool()
        self.signal_con = dataSignal()
        self.signal_con.data_received.connect(self.data_ready)       
        self.data = {}

        self.pandas_profile_button = QPushButton('Build Statistical Report')
        self.pandas_profile_button.setToolTip('Creates an HTML file containing a statistical breakdown of selected data')
        self.pandas_profile_button.setEnabled(False)
        self.pandas_profile_button.clicked.connect(self.pandas_report_th)

    @Slot()
    def data_ready(self, info):
        self.progress_bar.setValue(100)
        self.console.append(info)

    def cb(self, info):
        self.signal_con.data_received.emit(info)
    
    def pandas_report_th(self):
        self.threadpool.start(self.pandas_report)

    def pandas_report(self):
        # This one essentially odes the same thing, read a csv and process it for some actions, it goes one thread farther
          
        df = pd.read_csv(file
        self.data[file]) = df

        self.threadpool.start(self.pandas_report5(self.cb))
    def pandas_report5(self, callback):
      
        prof = ProfileReport(self.data[file])
      
        filename = file.replace('.txt', ' Statistical Report.html')
      
        prof.to_file(output_file=filename)
      
        print('Report done')
      
        result = 'Your report has been saved at: ' + filename
      
        callback(result)

SGaist

So the one that creates a file is working but the one that changes a GUI element freezes ? Do I get you correctly ?