def show_kv(self, instance, value):

        self.screen_manager.current = value

        child = self.screen_manager.current_screen.children[0]
        with open(child.kv_file, 'rb') as file:
            self.language_box.text = file.read().decode('utf8')
        Clock.unschedule(self.change_kv)
        self.change_kv()
        # reset undo/redo history
        self.language_box.reset_undo()
Called when an a item is selected, we need to show the .kv language
dataset/ETHPy150Open kivy/kivy/examples/demo/kivycatalog/main.py/Catalog.show_kv