PyQt connecting signal between sub class and parent class

Question

I want create a simple button to trigger some task. I was using PyQt designer to built GUI and trying to follow the advice that do not edit the UI module directly but put my customized code in a separate module then inherit all GUI aspects.

This is my GUI class:

from PyQt5 import QtCore, QtGui, QtWidgets


class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(507, 424)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.pushButton = QtWidgets.QPushButton(self.centralwidget)
        self.pushButton.setGeometry(QtCore.QRect(220, 350, 75, 23))
        self.pushButton.setObjectName("pushButton")
        MainWindow.setCentralWidget(self.centralwidget)


        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))
        self.pushButton.setText(_translate("MainWindow", "PushButton"))

This is my custom module:

from PyQt5 import QtCore,QtGui,QtWidgets

# main.py is the GUI module
import main 


class mainWindow(mainTest.Ui_MainWindow):
    def __init__(self):
        super().__init__()
        self.setupUi(self)

        # I want click this button and print something
        self.pushButton.clicked.connect(self.connectionTest)


    def connectionTest(self):
        print('connected')

if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    MainWindow = QtWidgets.QMainWindow()
    ui = mainTest.Ui_MainWindow()
    ui.setupUi(MainWindow)
    MainWindow.show()
    sys.exit(app.exec_())

Now my problem is when I run the module and click the pushbutton, it does not trigger the print method. However, if I directly add my custom code in GUI module it will work. I think there's something wrong with the inheritance and I do feel a bit confused about that.So what's the problem here?

change `MainWindow = QtWidgets.QMainWindow()` `ui = mainTest.Ui_MainWindow()` `ui.setupUi(MainWindow)` `MainWindow.show()` to `w = mainWindow()` `w.show()` — eyllanesc, Nov 23 '20 at 03:31
also change to `class mainWindow(QtWidgets.QMainWindow, mainTest.Ui_MainWindow):` — eyllanesc, Nov 23 '20 at 03:42

score 0 · Accepted Answer · answered Nov 23 '20 at 03:41

You are not using your mainWindow subclass at all, and even if you were, it should also inherit from QMainWindow.

class MainWindow(QtWidgets.QMainWindow, mainTest.Ui_MainWindow):
    def __init__(self):
        # ...

if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    window = MainWindow()
    window.show()
    sys.exit(app.exec_())

Please note the casing I changed for the MainWindow class: it is standard convention to name all classes with Capitalized names, as only variables and functions should have lower cased names (read more on the official Style Guide for Python Code).

PyQt connecting signal between sub class and parent class

1 Answers1