def close(self):
		'''关闭与数据库的连接'''
		if VERBOSE:
			print 'Database connection CLOSE.'
		self.conn.close()
def _invert_results(self, candidates):
        inverted_candidates = list(self.directory)

        for candidate in candidates:
            try:
                inverted_candidates.remove(candidate)
            except ValueError:
                pass

        return inverted_candidates