Python: 'PyQt5.QtCore.pyqtSignal' object has no attribute 'connect'

Question

I'm having an issue with a pyqtSignal going through threads. I get the following error :

AttributeError: 'PyQt5.QtCore.pyqtSignal' object has no attribute 'connect'

on the command :

 CALCULS_AE.Uni_finished.connect(self.getFinishThread())

The program is basically a mainwindow designed with PyQt Designer and calling a few different functions through threads. I want to get the finish signal of some threads in my MainWindow code (in order to show the results, etc...). Below is a little part of the code to explain its architecture.

Main Code :

class MainWindow(QMainWindow, Ui_MainWindow):

   def __init__(self):
       #Some code...
       self.Button.clicked.connect(self.launch_Calculation_clicked)

   def launch_Calculation(self):
       AE_Uni_thread = threading.Thread(target = CALCULS_AE.Calcul_AE_Uni, args = (arg1, arg2, arg3, arg4)) # Calculs_AE is a class defined in another file
       CALCULS_AE.Uni_finished.connect(self.getFinishThread()) # Another function doing some other stuff with the thread's results
       AE_Uni_thread.start()

Class CALCULS_AE which start the calculation :

class CALCULS_AE(object):
 #Signals
    Uni_finished = QtCore.pyqtSignal()
    Reb_finished = QtCore.pyqtSignal()

    def __init__(self):
        # Some Code

    def Calculs_AE_Uni(self, arg1, arg2, arg3, arg4):
        # Some Code launching the calculation
        self.Uni_finished.emit()

PS : pyqtSignals are defined on class level as specified in the documentation.

Thanks !

Answer 1

You have the following errors:

• you must create a Calculs object: self.calculs = Calculs()

• If you are going to use the native threading of Python it does not make sense to use QThread, there are 2 elements that do the same so change the QThread to QObject.

• When you connect a signal to a function you must pass the name of the function, not the evaluated function.

incorrect

[...].finished.connect(self.getFinishThread())

Right

[...].finished.connect(self.getFinishThread)

• target expects the name of the function, not the evaluated function.

• If you are not going to modify the constructor of the Calculs class, it is not necessary to implement it.

Code:

class Test(QtWidgets.QMainWindow, Ui_MainWindow):
    def __init__(self):
        super().__init__()
        Ui_MainWindow.__init__(self)
        self.setupUi(self)      
        self.pushButton.clicked.connect(self.Launch_Test)

    def Launch_Test(self):
        self.calculs = Calculs()
        self.calculs.finished.connect(self.getFinishThread)
        test_thread = threading.Thread(target = self.calculs.Calcul_Test)
        test_thread.start()

    def getFinishThread(self):
        print('Good ! \n')
        #os.system('pause')

class Calculs(QObject):
    finished = pyqtSignal()

    def Calcul_Test(self):
        print('Test calcul\n')
        self.finished.emit()