def __del__(self):
        """
        清理引用
        """
        self._connection = None
        self._engine = None
        self._transaction = None
        self._weak_results = None
        self._dialect = None
def __del__ ( self ) : self . _connection = None self . _engine = None self . _transaction = None self . _weak_results = None self . _dialect = None
清理引用