sqlalchemy.ext.mutable.MutableBase

class documentation

class MutableBase: (source)

Known subclasses: sqlalchemy.ext.mutable.Mutable, sqlalchemy.ext.mutable.MutableComposite

Common base class to :class:`.Mutable` and :class:`.MutableComposite`.

Class Method	`coerce`	Given a value, coerce it into the target type.
Class Method	`_get_listen_keys`	Given a descriptor attribute, return a ``set()`` of the attribute keys which indicate a change in the state of this attribute.
Class Method	`_listen_on_attribute`	Establish this type as a mutation listener for the given mapped descriptor.
Property	`_parents`	Dictionary of parent object's :class:`.InstanceState`->attribute name on the parent.

@classmethod
def coerce(cls, key: str, value: Any) -> Optional[Any]: (source) ¶

overridden in sqlalchemy.ext.mutable.MutableDict, sqlalchemy.ext.mutable.MutableList, sqlalchemy.ext.mutable.MutableSet

Given a value, coerce it into the target type. Can be overridden by custom subclasses to coerce incoming data into a particular type. By default, raises ``ValueError``. This method is called in different scenarios depending on if the parent class is of type :class:`.Mutable` or of type :class:`.MutableComposite`. In the case of the former, it is called for both attribute-set operations as well as during ORM loading operations. For the latter, it is only called during attribute-set operations; the mechanics of the :func:`.composite` construct handle coercion during load operations. :param key: string name of the ORM-mapped attribute being set. :param value: the incoming value. :return: the method should return the coerced value, or raise ``ValueError`` if the coercion cannot be completed.

@classmethod
def _get_listen_keys(cls, attribute: QueryableAttribute[Any]) -> Set[str]: (source) ¶

overridden in sqlalchemy.ext.mutable.MutableComposite

Given a descriptor attribute, return a ``set()`` of the attribute keys which indicate a change in the state of this attribute. This is normally just ``set([attribute.key])``, but can be overridden to provide for additional keys. E.g. a :class:`.MutableComposite` augments this set with the attribute keys associated with the columns that comprise the composite value. This collection is consulted in the case of intercepting the :meth:`.InstanceEvents.refresh` and :meth:`.InstanceEvents.refresh_flush` events, which pass along a list of attribute names that have been refreshed; the list is compared against this set to determine if action needs to be taken. .. versionadded:: 1.0.5

@classmethod
def _listen_on_attribute(cls, attribute: QueryableAttribute[Any], coerce: bool, parent_cls: _ExternalEntityType[Any]): (source) ¶

Establish this type as a mutation listener for the given mapped descriptor.

@memoized_property
_parents: WeakKeyDictionary[Any, Any] = (source) ¶

Dictionary of parent object's :class:`.InstanceState`->attribute name on the parent. This attribute is a so-called "memoized" property. It initializes itself with a new ``weakref.WeakKeyDictionary`` the first time it is accessed, returning the same object upon subsequent access. .. versionchanged:: 1.4 the :class:`.InstanceState` is now used as the key in the weak dictionary rather than the instance itself.