def sort_by(self, col, descending):
        """
        sort tree contents when a column header is clicked
        """
        # grab values to sort
        data = [(self.interior.set(child_ID, col), child_ID) for child_ID in self.interior.get_children('')]
        
        # if the data to be sorted is numeric change to float
        try:
            data = [(float(number), child_ID) for number, child_ID in data]
        except ValueError:
            pass

        # now sort the data in place
        data.sort(reverse=descending)
        for idx, item in enumerate(data):
            self.interior.move(item[1], '', idx)

        # switch the heading so that it will sort in the opposite direction
        self.interior.heading(col, command=lambda col=col: self.sort_by(col, not descending))
        
        if self._stripped_rows:
            list_of_items = self.interior.get_children('')
            for i in range(len(list_of_items)):
                self.interior.tag_configure(list_of_items[i], background=self._stripped_rows[i%2])

        sort tree contents when a column header is clicked
        
recipes/Python/580746_Tkinter_treeview_like_table_or_multicolumn/recipe-580746.py