elements.py 文件源码

def __init__(self, *clauses, **kw):
        """Return a :class:`.Tuple`.

        Main usage is to produce a composite IN construct::

            from sqlalchemy import tuple_

            tuple_(table.c.col1, table.c.col2).in_(
                [(1, 2), (5, 12), (10, 19)]
            )

        .. warning::

            The composite IN construct is not supported by all backends,
            and is currently known to work on Postgresql and MySQL,
            but not SQLite.   Unsupported backends will raise
            a subclass of :class:`~sqlalchemy.exc.DBAPIError` when such
            an expression is invoked.

        """

        clauses = [_literal_as_binds(c) for c in clauses]
        self._type_tuple = [arg.type for arg in clauses]
        self.type = kw.pop('type_', self._type_tuple[0]
                           if self._type_tuple else type_api.NULLTYPE)

        super(Tuple, self).__init__(*clauses, **kw)