Method __init__

lib/sqlalchemy/orm/decl_api.py:1160–1226

r"""Construct a new :class:`_orm.registry` :param metadata: An optional :class:`_schema.MetaData` instance. All :class:`_schema.Table` objects generated using declarative table mapping will make use of this :class:`_schema.MetaData` collection. If t

(
        self,
        *,
        metadata: Optional[MetaData] = None,
        class_registry: Optional[clsregistry._ClsRegistryType] = None,
        type_annotation_map: Optional[_TypeAnnotationMapType] = None,
        constructor: Callable[..., None] = _declarative_constructor,
    )

    _new_mappers: bool

    def __init__(
        self,
        *,
        metadata: Optional[MetaData] = None,
        class_registry: Optional[clsregistry._ClsRegistryType] = None,
        type_annotation_map: Optional[_TypeAnnotationMapType] = None,
        constructor: Callable[..., None] = _declarative_constructor,
    ):
        r"""Construct a new :class:`_orm.registry`

        :param metadata:
          An optional :class:`_schema.MetaData` instance.  All
          :class:`_schema.Table` objects generated using declarative
          table mapping will make use of this :class:`_schema.MetaData`
          collection.  If this argument is left at its default of ``None``,
          a blank :class:`_schema.MetaData` collection is created.

        :param constructor:
          Specify the implementation for the ``__init__`` function on a mapped
          class that has no ``__init__`` of its own.  Defaults to an
          implementation that assigns \**kwargs for declared
          fields and relationships to an instance.  If ``None`` is supplied,
          no __init__ will be provided and construction will fall back to
          cls.__init__ by way of the normal Python semantics.

        :param class_registry: optional dictionary that will serve as the
          registry of class names-> mapped classes when string names
          are used to identify classes inside of :func:`_orm.relationship`
          and others.  Allows two or more declarative base classes
          to share the same registry of class names for simplified
          inter-base relationships.

        :param type_annotation_map: optional dictionary of Python types to
          SQLAlchemy :class:`_types.TypeEngine` classes or instances.
          The provided dict will update the default type mapping.  This
          is used exclusively by the :class:`_orm.MappedColumn` construct
          to produce column types based on annotations within the
          :class:`_orm.Mapped` type.

          .. versionadded:: 2.0

          .. seealso::

              :ref:`orm_declarative_mapped_column_type_map`


        """
        lcl_metadata = metadata or MetaData()

        if class_registry is None:
            class_registry = weakref.WeakValueDictionary()

        self._class_registry = class_registry
        self._managers = weakref.WeakKeyDictionary()
        self._non_primary_mappers = weakref.WeakKeyDictionary()
        self.metadata = lcl_metadata
        self.constructor = constructor
        self.type_annotation_map = {}