import sys from PyQt5 import QtWidgets, uic from PyQt5.QtWidgets import QMainWindow from MainWindow import Ui_MainWindow class MainWindow(QMainWindow, Ui_MainWindow): def __init__(self, *args, **kwargs): super(MainWindow, self).__init__(*args, **kwargs) self.setupUi(self) def mainwindow_setup(w): w.setTitle("MainWindow Title") if __name__ == '__main__': app = QtWidgets.QApplication(sys.argv) # window = uic.loadUi("mainwindow.ui") # mainwindow_setup(window) window = MainWindow() window.show() app.exec()