def perform1(self): try: if (self.combo1.currentIndex() == 0 or self.combo2.currentIndex() == 0): QMessageBox.question(self, 'Warning!!', "Please Choose Valid Choice!", QMessageBox.NoButton) else: country1 = self.combo1.currentText() country2 = self.combo2.currentText() year = self.combo3.currentText() Graphs.Graph2(self, country1, country2, year) except BaseException as ex: print(ex)