ops.py 文件源码

def upgrade_ops(self):
        """An instance of :class:`.UpgradeOps`.

        .. seealso::

            :attr:`.MigrationScript.upgrade_ops_list`
        """
        if len(self._upgrade_ops) > 1:
            raise ValueError(
                "This MigrationScript instance has a multiple-entry "
                "list for UpgradeOps; please use the "
                "upgrade_ops_list attribute.")
        elif not self._upgrade_ops:
            return None
        else:
            return self._upgrade_ops[0]