Method generate_base

lib/sqlalchemy/orm/decl_api.py:1508–1611

Generate a declarative base class. Classes that inherit from the returned class object will be automatically mapped using declarative mapping. E.g.:: from sqlalchemy.orm import registry mapper_registry = registry() Base = mapper_regist

(
        self,
        mapper: Optional[Callable[..., Mapper[Any]]] = None,
        cls: Type[Any] = object,
        name: str = "Base",
        metaclass: Type[Any] = DeclarativeMeta,
    )

        instrumentation._instrumentation_factory.unregister(class_)

    def generate_base(
        self,
        mapper: Optional[Callable[..., Mapper[Any]]] = None,
        cls: Type[Any] = object,
        name: str = "Base",
        metaclass: Type[Any] = DeclarativeMeta,
    ) -> Any:
        """Generate a declarative base class.

        Classes that inherit from the returned class object will be
        automatically mapped using declarative mapping.

        E.g.::

            from sqlalchemy.orm import registry

            mapper_registry = registry()

            Base = mapper_registry.generate_base()


            class MyClass(Base):
                __tablename__ = "my_table"
                id = Column(Integer, primary_key=True)

        The above dynamically generated class is equivalent to the
        non-dynamic example below::

            from sqlalchemy.orm import registry
            from sqlalchemy.orm.decl_api import DeclarativeMeta

            mapper_registry = registry()


            class Base(metaclass=DeclarativeMeta):
                __abstract__ = True
                registry = mapper_registry
                metadata = mapper_registry.metadata

                __init__ = mapper_registry.constructor

        .. versionchanged:: 2.0 Note that the
           :meth:`_orm.registry.generate_base` method is superseded by the new
           :class:`_orm.DeclarativeBase` class, which generates a new "base"
           class using subclassing, rather than return value of a function.
           This allows an approach that is compatible with :pep:`484` typing
           tools.

        The :meth:`_orm.registry.generate_base` method provides the
        implementation for the :func:`_orm.declarative_base` function, which
        creates the :class:`_orm.registry` and base class all at once.

        See the section :ref:`orm_declarative_mapping` for background and
        examples.

        :param mapper:
          An optional callable, defaults to :class:`_orm.Mapper`.
          This function is used to generate new :class:`_orm.Mapper` objects.