That's a good idea, you mean the following ? 
thanks 
    if self.current_col == NULL:
            raise MemoryError()
        if self.tmp_indices == NULL:
            raise MemoryError()
        if self.hyper_indices == NULL:
            raise MemoryError()
        if self.index_to_color == NULL:
            raise MemoryError()
 self.current_col = current_col
        self.tmp_indices = tmp_indices
        self.hyper_indices = hyper_indices
        self.index_to_color = index_to_color