Sorts selection (or grid if none) corresponding to column of key

def sort_ascending(self, key):
        """Sorts selection (or grid if none) corresponding to column of key"""

        row, col, tab = key

        scells = self.grid.code_array[:, col, tab]

        def sorter(i):
            sorted_ele = scells[i]
            return sorted_ele is None, sorted_ele

        sorted_row_idxs = sorted(xrange(len(scells)), key=sorter)

        self.replace_cells(key, sorted_row_idxs)

        self.grid.ForceRefresh()