def create_window(self):
    self.windows.append(ChildWindow())


class ChildWindow(QMainWindow):

    def __init__(self, parent=None):
        super(ChildWindow, self).__init__(parent)
self.show()
if __name__ == '__main__':
    app = QApplication(sys.argv)
ex = MainWindow()
ex.show()
sys.exit(app.exec_())
Multiprocessing with Qt works in windows but not linux