class MainWindow(QtWidgets.QMainWindow):

    def __init__(self, parent=None):

        super(MainWindow, self).__init__(parent=parent)

        ui = Ui_MainWindow()

        ui.setupUi(self)

import sys

if __name__ == "__main__":

    app = QtWidgets.QApplication(sys.argv)

    w = MainWindow()

    w.show()

    sys.exit(app.exec_())