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Classe « Session »

Méthode sqlalchemy.orm.Session.get

Signature de la méthode get

def get(self, entity: '_EntityBindKey[_O]', ident: '_PKIdentityArgument', *, options: 'Optional[Sequence[ORMOption]]' = None, populate_existing: 'bool' = False, with_for_update: 'ForUpdateParameter' = None, identity_token: 'Optional[Any]' = None, execution_options: 'OrmExecuteOptionsParameter' = immutabledict({}), bind_arguments: 'Optional[_BindArguments]' = None) -> 'Optional[_O]' 

Description

help(Session.get)

Return an instance based on the given primary key identifier,
or ``None`` if not found.

E.g.::

    my_user = session.get(User, 5)

    some_object = session.get(VersionedFoo, (5, 10))

    some_object = session.get(VersionedFoo, {"id": 5, "version_id": 10})

.. versionadded:: 1.4 Added :meth:`_orm.Session.get`, which is moved
   from the now legacy :meth:`_orm.Query.get` method.

:meth:`_orm.Session.get` is special in that it provides direct
access to the identity map of the :class:`.Session`.
If the given primary key identifier is present
in the local identity map, the object is returned
directly from this collection and no SQL is emitted,
unless the object has been marked fully expired.
If not present,
a SELECT is performed in order to locate the object.

:meth:`_orm.Session.get` also will perform a check if
the object is present in the identity map and
marked as expired - a SELECT
is emitted to refresh the object as well as to
ensure that the row is still present.
If not, :class:`~sqlalchemy.orm.exc.ObjectDeletedError` is raised.

:param entity: a mapped class or :class:`.Mapper` indicating the
 type of entity to be loaded.

:param ident: A scalar, tuple, or dictionary representing the
 primary key.  For a composite (e.g. multiple column) primary key,
 a tuple or dictionary should be passed.

 For a single-column primary key, the scalar calling form is typically
 the most expedient.  If the primary key of a row is the value "5",
 the call looks like::

    my_object = session.get(SomeClass, 5)

 The tuple form contains primary key values typically in
 the order in which they correspond to the mapped
 :class:`_schema.Table`
 object's primary key columns, or if the
 :paramref:`_orm.Mapper.primary_key` configuration parameter were
 used, in
 the order used for that parameter. For example, if the primary key
 of a row is represented by the integer
 digits "5, 10" the call would look like::

     my_object = session.get(SomeClass, (5, 10))

 The dictionary form should include as keys the mapped attribute names
 corresponding to each element of the primary key.  If the mapped class
 has the attributes ``id``, ``version_id`` as the attributes which
 store the object's primary key value, the call would look like::

    my_object = session.get(SomeClass, {"id": 5, "version_id": 10})

:param options: optional sequence of loader options which will be
 applied to the query, if one is emitted.

:param populate_existing: causes the method to unconditionally emit
 a SQL query and refresh the object with the newly loaded data,
 regardless of whether or not the object is already present.

:param with_for_update: optional boolean ``True`` indicating FOR UPDATE
  should be used, or may be a dictionary containing flags to
  indicate a more specific set of FOR UPDATE flags for the SELECT;
  flags should match the parameters of
  :meth:`_query.Query.with_for_update`.
  Supersedes the :paramref:`.Session.refresh.lockmode` parameter.

:param execution_options: optional dictionary of execution options,
 which will be associated with the query execution if one is emitted.
 This dictionary can provide a subset of the options that are
 accepted by :meth:`_engine.Connection.execution_options`, and may
 also provide additional options understood only in an ORM context.

 .. versionadded:: 1.4.29

 .. seealso::

    :ref:`orm_queryguide_execution_options` - ORM-specific execution
    options

:param bind_arguments: dictionary of additional arguments to determine
 the bind.  May include "mapper", "bind", or other custom arguments.
 Contents of this dictionary are passed to the
 :meth:`.Session.get_bind` method.

 .. versionadded: 2.0.0rc1

:return: The object instance, or ``None``.

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