gistfile1.txt

    def delete_data_item(self, item):
        if item in self.data:
            index = self.data.index(item)
            if item in self.selection:
                self.dispatch('on_selection_change')
            self.data.remove(item)
            self.dispatch('on_data_item_delete', index)

    def delete_data_item_at_index(self, index):
        if 0 <= index < len(self.data):
            item = self.data[index]
            if item in self.selection:
                self.dispatch('on_selection_change')
            self.data.remove(item)
            self.dispatch('on_data_item_delete', index)

    def add_data_item(self, item):
        self.data.append(item)
        self.dispatch('on_data_item_add', len(self.data)-1)

    def add_data_item_at_index(self, index, item):
        self.data.insert(index, item)
        self.dispatch('on_data_item_add', index)

    def move_data_item(self, old_index, new_index):
        self.data.insert(newindex, self.data.pop(oldindex))
        self.dispatch('on_data_item_move', (old_index, new_index))