Function ordering_list

lib/sqlalchemy/ext/orderinglist.py:155–200

Prepares an :class:`OrderingList` factory for use in mapper definitions. Returns an object suitable for use as an argument to a Mapper relationship's ``collection_class`` option. e.g.:: from sqlalchemy.ext.orderinglist import ordering_list class Slide(Base):

(
    attr: str,
    count_from: Optional[int] = None,
    ordering_func: Optional[OrderingFunc[_T]] = None,
    reorder_on_append: bool = False,
)

def ordering_list(
    attr: str,
    count_from: Optional[int] = None,
    ordering_func: Optional[OrderingFunc[_T]] = None,
    reorder_on_append: bool = False,
) -> Callable[[], OrderingList[_T]]:
    """Prepares an :class:`OrderingList` factory for use in mapper definitions.

    Returns an object suitable for use as an argument to a Mapper
    relationship's ``collection_class`` option.  e.g.::

        from sqlalchemy.ext.orderinglist import ordering_list


        class Slide(Base):
            __tablename__ = "slide"

            id = Column(Integer, primary_key=True)
            name = Column(String)

            bullets = relationship(
                "Bullet",
                order_by="Bullet.position",
                collection_class=ordering_list("position"),
            )

    :param attr:
      Name of the mapped attribute to use for storage and retrieval of
      ordering information

    :param count_from:
      Set up an integer-based ordering, starting at ``count_from``.  For
      example, ``ordering_list('pos', count_from=1)`` would create a 1-based
      list in SQL, storing the value in the 'pos' column.  Ignored if
      ``ordering_func`` is supplied.

    Additional arguments are passed to the :class:`.OrderingList` constructor.

    """

    kw = _unsugar_count_from(
        count_from=count_from,
        ordering_func=ordering_func,
        reorder_on_append=reorder_on_append,
    )
    return lambda: OrderingList(attr, **kw)


# Ordering utility functions