Module « sqlalchemy.orm »

Fonction declarative_base - module sqlalchemy.orm

Signature de la fonction declarative_base

def declarative_base(bind=None, metadata=None, mapper=None, cls=<class 'object'>, name='Base', constructor=<function _declarative_constructor at 0x7f40cb7f5090>, class_registry=None, metaclass=<class 'sqlalchemy.orm.decl_api.DeclarativeMeta'>) 

Description

declarative_base.__doc__

Construct a base class for declarative class definitions.

    The new base class will be given a metaclass that produces
    appropriate :class:`~sqlalchemy.schema.Table` objects and makes
    the appropriate :func:`~sqlalchemy.orm.mapper` calls based on the
    information provided declaratively in the class and any subclasses
    of the class.

    The :func:`_orm.declarative_base` function is a shorthand version
    of using the :meth:`_orm.registry.generate_base`
    method.  That is, the following::

        from sqlalchemy.orm import declarative_base

        Base = declarative_base()

    Is equivalent to::

        from sqlalchemy.orm import registry

        mapper_registry = registry()
        Base = mapper_registry.generate_base()

    See the docstring for :class:`_orm.registry`
    and :meth:`_orm.registry.generate_base`
    for more details.

    .. versionchanged:: 1.4  The :func:`_orm.declarative_base`
       function is now a specialization of the more generic
       :class:`_orm.registry` class.  The function also moves to the
       ``sqlalchemy.orm`` package from the ``declarative.ext`` package.


    :param bind: An optional
      :class:`~sqlalchemy.engine.Connectable`, will be assigned
      the ``bind`` attribute on the :class:`~sqlalchemy.schema.MetaData`
      instance.

      .. deprecated:: 1.4  The "bind" argument to declarative_base is
         deprecated and will be removed in SQLAlchemy 2.0.

    :param metadata:
      An optional :class:`~sqlalchemy.schema.MetaData` instance.  All
      :class:`~sqlalchemy.schema.Table` objects implicitly declared by
      subclasses of the base will share this MetaData.  A MetaData instance
      will be created if none is provided.  The
      :class:`~sqlalchemy.schema.MetaData` instance will be available via the
      ``metadata`` attribute of the generated declarative base class.

    :param mapper:
      An optional callable, defaults to :func:`~sqlalchemy.orm.mapper`. Will
      be used to map subclasses to their Tables.

    :param cls:
      Defaults to :class:`object`. A type to use as the base for the generated
      declarative base class. May be a class or tuple of classes.

    :param name:
      Defaults to ``Base``.  The display name for the generated
      class.  Customizing this is not required, but can improve clarity in
      tracebacks and debugging.

    :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 metaclass:
      Defaults to :class:`.DeclarativeMeta`.  A metaclass or __metaclass__
      compatible callable to use as the meta type of the generated
      declarative base class.

    .. seealso::

        :class:`_orm.registry`