# Objetos de referencia débil

Python soporta referencias débiles como objetos de primera clase. Hay dos tipos de objetos específicos que implementan directamente referencias débiles. El primero es un objeto con referencia simple, y el segundo actúa como un proxy del objeto original tanto como pueda.

int PyWeakref_Check( PyObject *ob)

  Retorna verdadero (true) si ob es una referencia o un objeto proxy. Esta función siempre finaliza con éxito.

int PyWeakref_CheckRef( PyObject *ob)

  Retorna verdadero (true) si ob es un objeto de referencia. Esta función siempre finaliza con éxito.

int PyWeakref_CheckProxy( PyObject *ob)

  Retorna verdadero (true) si ob es un objeto proxy. Esta función siempre finaliza con éxito.

PyObject *PyWeakref_NewRef( PyObject *ob, PyObject *callback)
  Return value: New reference. Part of the Stable ABI.

  Return a weak reference object for the object ob. This will always return a new reference, but is not guaranteed to create a new object; an existing reference object may be returned. The second parameter, callback, can be a callable object that receives notification when ob is garbage collected; it should accept a single parameter, which will be the weak reference object itself. callback may also be `None` or `NULL`. If ob is not a weakly referencable object, or if callback is not callable, `None`, or `NULL`, this will return `NULL` and raise `TypeError`.

PyObject *PyWeakref_NewProxy( PyObject *ob, PyObject *callback)
  Return value: New reference. Part of the Stable ABI.

  Return a weak reference proxy object for the object ob. This will always return a new reference, but is not guaranteed to create a new object; an existing proxy object may be returned. The second parameter, callback, can be a callable object that receives notification when ob is garbage collected; it should accept a single parameter, which will be the weak reference object itself. callback may also be `None` or `NULL`. If ob is not a weakly referencable object, or if callback is not callable, `None`, or `NULL`, this will return `NULL` and raise `TypeError`.

PyObject *PyWeakref_GetObject( PyObject *ref)
  Return value: Borrowed reference. Part of the Stable ABI.

  Return the referenced object from a weak reference, ref. If the referent is no longer live, returns `Py_None`.

  Nota

  Esta función retorna una referencia borrowed reference al objeto referenciado. Esto significa que siempre debe llamar a `Py_INCREF()` sobre el objeto, excepto cuando no pueda ser destruido antes del último uso de la referencia prestada.

PyObject *PyWeakref_GET_OBJECT( PyObject *ref)
  Return value: Borrowed reference.

  Similar to `PyWeakref_GetObject()`, but does no error checking.

void PyObject_ClearWeakRefs( PyObject *object)
  Part of the Stable ABI.

  This function is called by the `tp_dealloc` handler to clear weak references.

  This iterates through the weak references for object and calls callbacks for those references which have one. It returns when all callbacks have been attempted.