Release: 1.2.19 | Release Date: April 15, 2019

# SQLAlchemy 1.2 Documentation

# ORM Exceptions

SQLAlchemy ORM exceptions.

`sqlalchemy.orm.exc.``ConcurrentModificationError`

  alias of `sqlalchemy.orm.exc.StaleDataError`

exception `sqlalchemy.orm.exc.``DetachedInstanceError`(*arg, **kw)

  An attempt to access unloaded attributes on a mapped instance that is detached.

exception `sqlalchemy.orm.exc.``FlushError`(*arg, **kw)

  A invalid condition was detected during flush().

exception `sqlalchemy.orm.exc.``MultipleResultsFound`(*arg, **kw)

  A single database result was required but more than one were found.

`sqlalchemy.orm.exc.``NO_STATE` = (<class 'AttributeError'>, <class 'KeyError'>)

  Exception types that may be raised by instrumentation implementations.

exception `sqlalchemy.orm.exc.``NoResultFound`(*arg, **kw)

  A database result was required but none was found.

exception `sqlalchemy.orm.exc.``ObjectDeletedError`(base, state, msg=None)

  A refresh operation failed to retrieve the database row corresponding to an object’s known primary key identity.

  A refresh operation proceeds when an expired attribute is accessed on an object, or when `Query.get()` is used to retrieve an object which is, upon retrieval, detected as expired. A SELECT is emitted for the target row based on primary key; if no row is returned, this exception is raised.

  The true meaning of this exception is simply that no row exists for the primary key identifier associated with a persistent object. The row may have been deleted, or in some cases the primary key updated to a new value, outside of the ORM’s management of the target object.

exception `sqlalchemy.orm.exc.``ObjectDereferencedError`(*arg, **kw)

  An operation cannot complete due to an object being garbage collected.

exception `sqlalchemy.orm.exc.``StaleDataError`(*arg, **kw)

  An operation encountered database state that is unaccounted for.

  Conditions which cause this to happen include:

  - A flush may have attempted to update or delete rows and an unexpected number of rows were matched during the UPDATE or DELETE statement. Note that when version_id_col is used, rows in UPDATE or DELETE statements are also matched against the current known version identifier.

  - A mapped object with version_id_col was refreshed, and the version number coming back from the database does not match that of the object itself.

  - A object is detached from its parent object, however the object was previously attached to a different parent identity which was garbage collected, and a decision cannot be made if the new parent was really the most recent “parent”.

exception `sqlalchemy.orm.exc.``UnmappedClassError`(cls, msg=None)

  An mapping operation was requested for an unknown class.

exception `sqlalchemy.orm.exc.``UnmappedColumnError`(*arg, **kw)

  Mapping operation was requested on an unknown column.

exception `sqlalchemy.orm.exc.``UnmappedError`(*arg, **kw)

  Base for exceptions that involve expected mappings not present.

exception `sqlalchemy.orm.exc.``UnmappedInstanceError`(base, obj, msg=None)

  An mapping operation was requested for an unknown instance.