Weak Reference Objects
**********************

Python supports *weak references* as first-class objects.  There are
two specific object types which directly implement weak references.
The first is a simple reference object, and the second acts as a proxy
for the original object as much as it can.

int PyWeakref_Check(PyObject *ob)

   Return non-zero if *ob* is either a reference or proxy object.
   This function always succeeds.

int PyWeakref_CheckRef(PyObject *ob)

   Return non-zero if *ob* is a reference object or a subclass of the
   reference type.  This function always succeeds.

int PyWeakref_CheckRefExact(PyObject *ob)

   Return non-zero if *ob* is a reference object, but not a subclass
   of the reference type.  This function always succeeds.

int PyWeakref_CheckProxy(PyObject *ob)

   Return non-zero if *ob* is a proxy object.  This function always
   succeeds.

PyObject *PyWeakref_NewRef(PyObject *ob, PyObject *callback)
    *Rückgabewert: neue Referenz.** Teil der 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 referenceable object, this will raise "TypeError" and return
   "NULL".

   Siehe auch:

     "PyType_SUPPORTS_WEAKREFS()" for checking if *ob* is weakly
     referenceable.

PyObject *PyWeakref_NewProxy(PyObject *ob, PyObject *callback)
    *Rückgabewert: neue Referenz.** Teil der 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* weakly
   referenceable object, this will raise "TypeError" and return
   "NULL".

   Siehe auch:

     "PyType_SUPPORTS_WEAKREFS()" for checking if *ob* is weakly
     referenceable.

int PyWeakref_GetRef(PyObject *ref, PyObject **pobj)
    * Teil der Stable ABI seit Version 3.13.*

   Get a *strong reference* to the referenced object from a weak
   reference, *ref*, into **pobj*.

   * On success, set **pobj* to a new *strong reference* to the
     referenced object and return 1.

   * If the reference is dead, set **pobj* to "NULL" and return 0.

   * On error, raise an exception and return -1.

   Added in version 3.13.

PyObject *PyWeakref_GetObject(PyObject *ref)
    *Rückgabewert: geliehene Referenz.** Teil der Stable ABI.*

   Return a *borrowed reference* to the referenced object from a weak
   reference, *ref*.  If the referent is no longer live, returns
   "Py_None".

   Bemerkung:

     This function returns a *borrowed reference* to the referenced
     object. This means that you should always call "Py_INCREF()" on
     the object except when it cannot be destroyed before the last
     usage of the borrowed reference.

   Veraltet seit Version 3.13, wird in Version 3.15 entfernt: Use
   "PyWeakref_GetRef()" instead.

PyObject *PyWeakref_GET_OBJECT(PyObject *ref)
    *Rückgabewert: geliehene Referenz.*

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

   Veraltet seit Version 3.13, wird in Version 3.15 entfernt: Use
   "PyWeakref_GetRef()" instead.

void PyObject_ClearWeakRefs(PyObject *object)
    * Teil der 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.

void PyUnstable_Object_ClearWeakRefsNoCallbacks(PyObject *object)

   *Dies ist Unstable API. Sie kann sich in Minor-Releases ohne
   Vorwarnung ändern.*

   Clears the weakrefs for *object* without calling the callbacks.

   This function is called by the "tp_dealloc" handler for types with
   finalizers (i.e., "__del__()").  The handler for those objects
   first calls "PyObject_ClearWeakRefs()" to clear weakrefs and call
   their callbacks, then the finalizer, and finally this function to
   clear any weakrefs that may have been created by the finalizer.

   In most circumstances, it's more appropriate to use
   "PyObject_ClearWeakRefs()" to clear weakrefs instead of this
   function.

   Added in version 3.13.
