# Protocolo de objeto

PyObject *Py_GetConstant(unsigned int constant_id)
  Part of the Stable ABI since version 3.13.

  Get a strong reference to a constant.

  Set an exception and return `NULL` if constant_id is invalid.

  constant_id must be one of these constant identifiers:

  Constant Identifier | Value | Returned object
  --- | --- | ---
  Py_CONSTANT_NONE | `0` | `None`
  Py_CONSTANT_FALSE | `1` | `False`
  Py_CONSTANT_TRUE | `2` | `True`
  Py_CONSTANT_ELLIPSIS | `3` | `Ellipsis`
  Py_CONSTANT_NOT_IMPLEMENTED | `4` | `NotImplemented`
  Py_CONSTANT_ZERO | `5` | `0`
  Py_CONSTANT_ONE | `6` | `1`
  Py_CONSTANT_EMPTY_STR | `7` | `''`
  Py_CONSTANT_EMPTY_BYTES | `8` | `b''`
  Py_CONSTANT_EMPTY_TUPLE | `9` | `()`

  Numeric values are only given for projects which cannot use the constant identifiers.

  Added in version 3.13.

  Detalles de implementación de CPython: In CPython, all of these constants are immortal.

PyObject *Py_GetConstantBorrowed(unsigned int constant_id)
  Part of the Stable ABI since version 3.13.

  Similar to `Py_GetConstant()`, but return a borrowed reference.

  This function is primarily intended for backwards compatibility: using `Py_GetConstant()` is recommended for new code.

  The reference is borrowed from the interpreter, and is valid until the interpreter finalization.

  Added in version 3.13.

PyObject *Py_NotImplemented

  El singleton `NotImplemented`, se usa para indicar que una operación no está implementada para la combinación de tipos dada.

Py_RETURN_NOTIMPLEMENTED

  Properly handle returning `Py_NotImplemented` from within a C function (that is, create a new strong reference to `NotImplemented` and return it).

Py_PRINT_RAW

  Flag to be used with multiple functions that print the object (like `PyObject_Print()` and `PyFile_WriteObject()`). If passed, these functions use the `str()` of the object instead of the `repr()`.

int PyObject_Print(PyObject *o, FILE *fp, int flags)

  Print an object o, on file fp. Returns `-1` on error. The flags argument is used to enable certain printing options. The only option currently supported is `Py_PRINT_RAW`; if given, the `str()` of the object is written instead of the `repr()`.

int PyObject_HasAttrWithError(PyObject *o, PyObject *attr_name)
  Part of the Stable ABI since version 3.13.

  Returns `1` if o has the attribute attr_name, and `0` otherwise. This is equivalent to the Python expression `hasattr(o, attr_name)`. On failure, return `-1`.

  Added in version 3.13.

int PyObject_HasAttrStringWithError(PyObject *o, const char *attr_name)
  Part of the Stable ABI since version 3.13.

  This is the same as `PyObject_HasAttrWithError()`, but attr_name is specified as a const char* UTF-8 encoded bytes string, rather than a PyObject*.

  Added in version 3.13.

int PyObject_HasAttr(PyObject *o, PyObject *attr_name)
  Part of the Stable ABI.

  Returns `1` if o has the attribute attr_name, and `0` otherwise. This function always succeeds.

  Nota

  Exceptions that occur when this calls `__getattr__()` and `__getattribute__()` methods aren’t propagated, but instead given to `sys.unraisablehook()`. For proper error handling, use `PyObject_HasAttrWithError()`, `PyObject_GetOptionalAttr()` or `PyObject_GetAttr()` instead.

int PyObject_HasAttrString(PyObject *o, const char *attr_name)
  Part of the Stable ABI.

  This is the same as `PyObject_HasAttr()`, but attr_name is specified as a const char* UTF-8 encoded bytes string, rather than a PyObject*.

  Nota

  Exceptions that occur when this calls `__getattr__()` and `__getattribute__()` methods or while creating the temporary `str` object are silently ignored. For proper error handling, use `PyObject_HasAttrStringWithError()`, `PyObject_GetOptionalAttrString()` or `PyObject_GetAttrString()` instead.

PyObject *PyObject_GetAttr(PyObject *o, PyObject *attr_name)
  Return value: New reference. Part of the Stable ABI.

  Recupera un atributo llamado attr_name del objeto o. Retorna el valor del atributo en caso de éxito o `NULL` en caso de error. Este es el equivalente de la expresión de Python `o.attr_name`.

  If the missing attribute should not be treated as a failure, you can use `PyObject_GetOptionalAttr()` instead.

PyObject *PyObject_GetAttrString(PyObject *o, const char *attr_name)
  Return value: New reference. Part of the Stable ABI.

  This is the same as `PyObject_GetAttr()`, but attr_name is specified as a const char* UTF-8 encoded bytes string, rather than a PyObject*.

  If the missing attribute should not be treated as a failure, you can use `PyObject_GetOptionalAttrString()` instead.

int PyObject_GetOptionalAttr(PyObject *obj, PyObject *attr_name, PyObject **result);
  Part of the Stable ABI since version 3.13.

  Variant of `PyObject_GetAttr()` which doesn’t raise `AttributeError` if the attribute is not found.

  If the attribute is found, return `1` and set *result to a new strong reference to the attribute. If the attribute is not found, return `0` and set *result to `NULL`; the `AttributeError` is silenced. If an error other than `AttributeError` is raised, return `-1` and set *result to `NULL`.

  Added in version 3.13.

int PyObject_GetOptionalAttrString(PyObject *obj, const char *attr_name, PyObject **result);
  Part of the Stable ABI since version 3.13.

  This is the same as `PyObject_GetOptionalAttr()`, but attr_name is specified as a const char* UTF-8 encoded bytes string, rather than a PyObject*.

  Added in version 3.13.

PyObject *PyObject_GenericGetAttr(PyObject *o, PyObject *name)
  Return value: New reference. Part of the Stable ABI.

  Función getter de atributo genérico que debe colocarse en la ranura `tp_getattro` de un objeto tipo. Busca un descriptor en el diccionario de clases en el MRO del objeto, así como un atributo en el objeto `__ dict__` (si está presente). Como se describe en Implementando descriptores, los descriptores de datos tienen preferencia sobre los atributos de instancia, mientras que los descriptores que no son de datos no lo hacen. De lo contrario, se lanza un `AttributeError`.

int PyObject_SetAttr(PyObject *o, PyObject *attr_name, PyObject *v)
  Part of the Stable ABI.

  Establece el valor del atributo llamado attr_name, para el objeto o, en el valor v. Lanza una excepción y retorna `-1` en caso de falla; retorna `0` en caso de éxito. Este es el equivalente de la declaración de Python `o.attr_name = v`.

  Si v es `NULL`, el atributo se elimina. Este comportamiento está deprecado en favor de usar `PyObject_DelAttr()`, pero por el momento no hay planes de quitarlo.

int PyObject_SetAttrString(PyObject *o, const char *attr_name, PyObject *v)
  Part of the Stable ABI.

  This is the same as `PyObject_SetAttr()`, but attr_name is specified as a const char* UTF-8 encoded bytes string, rather than a PyObject*.

  Si v es `NULL`, el atributo se elimina, sin embargo, esta característica está deprecada en favor de usar `PyObject_DelAttrString()`.

  The number of different attribute names passed to this function should be kept small, usually by using a statically allocated string as attr_name. For attribute names that aren’t known at compile time, prefer calling `PyUnicode_FromString()` and `PyObject_SetAttr()` directly. For more details, see `PyUnicode_InternFromString()`, which may be used internally to create a key object.

int PyObject_GenericSetAttr(PyObject *o, PyObject *name, PyObject *value)
  Part of the Stable ABI.

  Establecimiento de atributo genérico y función de eliminación que está destinada a colocarse en la ranura de un objeto tipo `tp_setattro`. Busca un descriptor de datos en el diccionario de clases en el MRO del objeto y, si se encuentra, tiene preferencia sobre la configuración o eliminación del atributo en el diccionario de instancias. De lo contrario, el atributo se establece o elimina en el objeto `__dict__` (si está presente). En caso de éxito, se retorna `0`; de lo contrario, se lanza un `AttributeError` y se retorna `-1`.

int PyObject_DelAttr(PyObject *o, PyObject *attr_name)
  Part of the Stable ABI since version 3.13.

  Elimina el atributo llamado attr_name, para el objeto o. Retorna `-1` en caso de falla. Este es el equivalente de la declaración de Python `del o.attr_name`.

int PyObject_DelAttrString(PyObject *o, const char *attr_name)
  Part of the Stable ABI since version 3.13.

  This is the same as `PyObject_DelAttr()`, but attr_name is specified as a const char* UTF-8 encoded bytes string, rather than a PyObject*.

  The number of different attribute names passed to this function should be kept small, usually by using a statically allocated string as attr_name. For attribute names that aren’t known at compile time, prefer calling `PyUnicode_FromString()` and `PyObject_DelAttr()` directly. For more details, see `PyUnicode_InternFromString()`, which may be used internally to create a key object for lookup.

PyObject *PyObject_GenericGetDict(PyObject *o, void *context)
  Return value: New reference. Part of the Stable ABI since version 3.10.

  Una implementación genérica para obtener un descriptor `__dict__`. Crea el diccionario si es necesario.

  Esta función también puede ser llamada para obtener el `__dict__` del objeto o. Se pasa context igual a `NULL` cuando se lo llama. Dado que esta función puede necesitar asignar memoria para el diccionario, puede ser más eficiente llamar a `PyObject_GetAttr()` para acceder a un atributo del objeto.

  En caso de fallo, retorna `NULL` con una excepción establecida.

  Added in version 3.3.

int PyObject_GenericSetDict(PyObject *o, PyObject *value, void *context)
  Part of the Stable ABI since version 3.7.

  Una implementación genérica para el creador de un descriptor `__dict__`. Esta implementación no permite que se elimine el diccionario.

  Added in version 3.3.

PyObject **_PyObject_GetDictPtr(PyObject *obj)

  Retorna un puntero al `__dict__` del objeto obj. Si no hay `__dict__`, retorna `NULL` sin establecer una excepción.

  Esta función puede necesitar asignar memoria para el diccionario, por lo que puede ser más eficiente llamar a `PyObject_GetAttr()` para acceder a un atributo del objeto.

PyObject *PyObject_RichCompare(PyObject *o1, PyObject *o2, int opid)
  Return value: New reference. Part of the Stable ABI.

  Compare the values of o1 and o2 using the operation specified by opid, which must be one of `Py_LT`, `Py_LE`, `Py_EQ`, `Py_NE`, `Py_GT`, or `Py_GE`, corresponding to `<`, `<=`, `==`, `!=`, `>`, or `>=` respectively. This is the equivalent of the Python expression `o1 op o2`, where `op` is the operator corresponding to opid. Returns the value of the comparison on success, or `NULL` on failure.

int PyObject_RichCompareBool(PyObject *o1, PyObject *o2, int opid)
  Part of the Stable ABI.

  Compare the values of o1 and o2 using the operation specified by opid, like `PyObject_RichCompare()`, but returns `-1` on error, `0` if the result is false, `1` otherwise.

Nota

If o1 and o2 are the same object, `PyObject_RichCompareBool()` will always return `1` for `Py_EQ` and `0` for `Py_NE`.

PyObject *PyObject_Format(PyObject *obj, PyObject *format_spec)
  Part of the Stable ABI.

  Format obj using format_spec. This is equivalent to the Python expression `format(obj, format_spec)`.

  format_spec may be `NULL`. In this case the call is equivalent to `format(obj)`. Returns the formatted string on success, `NULL` on failure.

PyObject *PyObject_Repr(PyObject *o)
  Return value: New reference. Part of the Stable ABI.

  Calcula una representación de cadena de caracteres del objeto o. Retorna la representación de cadena de caracteres en caso de éxito, `NULL` en caso de error. Este es el equivalente de la expresión de Python `repr(o)`. Llamado por la función incorporada `repr()`.

  Distinto en la versión 3.4: Esta función ahora incluye una afirmación de depuración para ayudar a garantizar que no descarte silenciosamente una excepción activa.

PyObject *PyObject_ASCII(PyObject *o)
  Return value: New reference. Part of the Stable ABI.

  Como `PyObject_Repr()`, calcula una representación de cadena de caracteres del objeto o, pero escapa los caracteres no ASCII en la cadena de caracteres retornada por `PyObject_Repr()` con `\x`, `\u` o `\U` escapa. Esto genera una cadena de caracteres similar a la que retorna `PyObject_Repr()` en Python 2. Llamado por la función incorporada `ascii()`.

PyObject *PyObject_Str(PyObject *o)
  Return value: New reference. Part of the Stable ABI.

  Calcula una representación de cadena de caracteres del objeto o. Retorna la representación de cadena de caracteres en caso de éxito, `NULL` en caso de error. Llamado por la función incorporada `str()` y, por lo tanto, por la función `print()`.

  Distinto en la versión 3.4: Esta función ahora incluye una afirmación de depuración para ayudar a garantizar que no descarte silenciosamente una excepción activa.

PyObject *PyObject_Bytes(PyObject *o)
  Return value: New reference. Part of the Stable ABI.

  Calcula una representación de bytes del objeto o. `NULL` se retorna en caso de error y un objeto de bytes en caso de éxito. Esto es equivalente a la expresión de Python `bytes(o)`, cuando o no es un número entero. A diferencia de `bytes(o)`, se lanza un TypeError cuando o es un entero en lugar de un objeto de bytes con inicialización cero.

int PyObject_IsSubclass(PyObject *derived, PyObject *cls)
  Part of the Stable ABI.

  Retorna `1` si la clase derived es idéntica o derivada de la clase cls; de lo contrario, retorna `0`. En caso de error, retorna `-1`.

  Si cls es una tupla, la verificación se realizará con cada entrada en cls. El resultado será `1` cuando al menos una de las verificaciones retorne `1`, de lo contrario será `0`.

  If cls has a `__subclasscheck__()` method, it will be called to determine the subclass status as described in PEP 3119. Otherwise, derived is a subclass of cls if it is a direct or indirect subclass, i.e. contained in `cls.__mro__`.

  Normally only class objects, i.e. instances of `type` or a derived class, are considered classes. However, objects can override this by having a `__bases__` attribute (which must be a tuple of base classes).

int PyObject_IsInstance(PyObject *inst, PyObject *cls)
  Part of the Stable ABI.

  Retorna `1` si inst es una instancia de la clase cls o una subclase de cls, o `0` si no. En caso de error, retorna `-1` y establece una excepción.

  Si cls es una tupla, la verificación se realizará con cada entrada en cls. El resultado será `1` cuando al menos una de las verificaciones retorne `1`, de lo contrario será `0`.

  If cls has a `__instancecheck__()` method, it will be called to determine the subclass status as described in PEP 3119. Otherwise, inst is an instance of cls if its class is a subclass of cls.

  An instance inst can override what is considered its class by having a `__class__` attribute.

  An object cls can override if it is considered a class, and what its base classes are, by having a `__bases__` attribute (which must be a tuple of base classes).

Py_hash_t PyObject_Hash(PyObject *o)
  Part of the Stable ABI.

  Calcula y retorna el valor hash de un objeto o. En caso de fallo, retorna `-1`. Este es el equivalente de la expresión de Python `hash(o)`.

  Distinto en la versión 3.2: El tipo de retorno ahora es Py_hash_t. Este es un entero con signo del mismo tamaño que `Py_ssize_t`.

Py_hash_t PyObject_HashNotImplemented(PyObject *o)
  Part of the Stable ABI.

  Set a `TypeError` indicating that `type(o)` is not hashable and return `-1`. This function receives special treatment when stored in a `tp_hash` slot, allowing a type to explicitly indicate to the interpreter that it is not hashable.

int PyObject_IsTrue(PyObject *o)
  Part of the Stable ABI.

  Retorna `1` si el objeto o se considera verdadero y `0` en caso contrario. Esto es equivalente a la expresión de Python `not not o`. En caso de error, retorna `-1`.

int PyObject_Not(PyObject *o)
  Part of the Stable ABI.

  Retorna `0` si el objeto o se considera verdadero, y `1` de lo contrario. Esto es equivalente a la expresión de Python `not o`. En caso de error, retorna `-1`.

PyObject *PyObject_Type(PyObject *o)
  Return value: New reference. Part of the Stable ABI.

  When o is non-`NULL`, returns a type object corresponding to the object type of object o. On failure, raises `SystemError` and returns `NULL`. This is equivalent to the Python expression `type(o)`. This function creates a new strong reference to the return value. There’s really no reason to use this function instead of the `Py_TYPE()` function, which returns a pointer of type PyTypeObject*, except when a new strong reference is needed.

int PyObject_TypeCheck(PyObject *o, PyTypeObject *type)

  Retorna un valor no-nulo si el objeto o es de tipo type o un subtipo de type, y `0` en cualquier otro caso. Ninguno de los dos parámetros debe ser `NULL`.

Py_ssize_t PyObject_Size(PyObject *o)
Py_ssize_t PyObject_Length(PyObject *o)
  Part of the Stable ABI.

  Retorna la longitud del objeto o. Si el objeto o proporciona los protocolos de secuencia y mapeo, se retorna la longitud de la secuencia. En caso de error, se retorna `-1`. Este es el equivalente a la expresión de Python `len(o)`.

Py_ssize_t PyObject_LengthHint(PyObject *o, Py_ssize_t defaultvalue)

  Retorna una longitud estimada para el objeto o. Primero intenta retornar su longitud real, luego una estimación usando `__length_hint__()`, y finalmente retorna el valor predeterminado. En caso de error, retorna `-1`. Este es el equivalente a la expresión de Python `operator.length_hint(o, defaultvalue)`.

  Added in version 3.4.

PyObject *PyObject_GetItem(PyObject *o, PyObject *key)
  Return value: New reference. Part of the Stable ABI.

  Retorna el elemento de o correspondiente a la clave key del objeto o `NULL` en caso de error. Este es el equivalente de la expresión de Python `o[key]`.

int PyObject_SetItem(PyObject *o, PyObject *key, PyObject *v)
  Part of the Stable ABI.

  Asigna el objeto key al valor v. Lanza una excepción y retorna `-1` en caso de error; retorna `0` en caso de éxito. Este es el equivalente de la declaración de Python `o[key] = v`. Esta función no roba una referencia a v.

int PyObject_DelItem(PyObject *o, PyObject *key)
  Part of the Stable ABI.

  Elimina la asignación para el objeto key del objeto o. Retorna `-1` en caso de falla. Esto es equivalente a la declaración de Python `del o[key]`.

int PyObject_DelItemString(PyObject *o, const char *key)
  Part of the Stable ABI.

  This is the same as `PyObject_DelItem()`, but key is specified as a const char* UTF-8 encoded bytes string, rather than a PyObject*.

PyObject *PyObject_Dir(PyObject *o)
  Return value: New reference. Part of the Stable ABI.

  Esto es equivalente a la expresión de Python `dir(o)`, que retorna una lista (posiblemente vacía) de cadenas de caracteres apropiadas para el argumento del objeto, o `NULL` si hubo un error. Si el argumento es `NULL`, es como el Python `dir()`, que retorna los nombres de los locales actuales; en este caso, si no hay un marco de ejecución activo, se retorna `NULL` pero `PyErr_Occurred()` retornará falso.

PyObject *PyObject_GetIter(PyObject *o)
  Return value: New reference. Part of the Stable ABI.

  Esto es equivalente a la expresión de Python `iter(o)`. Retorna un nuevo iterador para el argumento del objeto, o el propio objeto si el objeto ya es un iterador. Lanza `TypeError` y retorna `NULL` si el objeto no puede iterarse.

PyObject *PyObject_SelfIter(PyObject *obj)
  Return value: New reference. Part of the Stable ABI.

  This is equivalent to the Python `__iter__(self): return self` method. It is intended for iterator types, to be used in the `PyTypeObject.tp_iter` slot.

PyObject *PyObject_GetAIter(PyObject *o)
  Return value: New reference. Part of the Stable ABI since version 3.10.

  Esto es equivalente a la expresión de Python `aiter(o)`. Toma un objeto `AsyncIterable` y retorna `AsyncIterator`. Este es típicamente un nuevo iterador, pero si el argumento es `AsyncIterator`, se retornará a sí mismo. Lanza `TypeError` y retorna `NULL` si el objeto no puede ser iterado.

  Added in version 3.10.

void *PyObject_GetTypeData(PyObject *o, PyTypeObject *cls)
  Part of the Stable ABI since version 3.12.

  Get a pointer to subclass-specific data reserved for cls.

  The object o must be an instance of cls, and cls must have been created using negative `PyType_Spec.basicsize`. Python does not check this.

  On error, set an exception and return `NULL`.

  Added in version 3.12.

Py_ssize_t PyType_GetTypeDataSize(PyTypeObject *cls)
  Part of the Stable ABI since version 3.12.

  Return the size of the instance memory space reserved for cls, i.e. the size of the memory `PyObject_GetTypeData()` returns.

  This may be larger than requested using `-PyType_Spec.basicsize`; it is safe to use this larger size (e.g. with `memset()`).

  The type cls must have been created using negative `PyType_Spec.basicsize`. Python does not check this.

  On error, set an exception and return a negative value.

  Added in version 3.12.

void *PyObject_GetItemData(PyObject *o)

  Get a pointer to per-item data for a class with `Py_TPFLAGS_ITEMS_AT_END`.

  On error, set an exception and return `NULL`. `TypeError` is raised if o does not have `Py_TPFLAGS_ITEMS_AT_END` set.

  Added in version 3.12.

int PyObject_VisitManagedDict(PyObject *obj, visitproc visit, void *arg)

  Visit the managed dictionary of obj.

  This function must only be called in a traverse function of the type which has the `Py_TPFLAGS_MANAGED_DICT` flag set.

  Added in version 3.13.

void PyObject_ClearManagedDict(PyObject *obj)

  Clear the managed dictionary of obj.

  This function must only be called in a clear function of the type which has the `Py_TPFLAGS_MANAGED_DICT` flag set.

  Added in version 3.13.

int PyUnstable_Object_EnableDeferredRefcount(PyObject *obj)
  This is Unstable API. It may change without warning in minor releases.

  Enable deferred reference counting on obj, if supported by the runtime. In the free-threaded build, this allows the interpreter to avoid reference count adjustments to obj, which may improve multi-threaded performance. The tradeoff is that obj will only be deallocated by the tracing garbage collector, and not when the interpreter no longer has any references to it.

  This function returns `1` if deferred reference counting is enabled on obj, and `0` if deferred reference counting is not supported or if the hint was ignored by the interpreter, such as when deferred reference counting is already enabled on obj. This function is thread-safe, and cannot fail.

  This function does nothing on builds with the GIL enabled, which do not support deferred reference counting. This also does nothing if obj is not an object tracked by the garbage collector (see `gc.is_tracked()` and `PyObject_GC_IsTracked()`).

  This function is intended to be used soon after obj is created, by the code that creates it, such as in the object’s `tp_new` slot.

  Added in version 3.14.

int PyUnstable_Object_IsUniqueReferencedTemporary(PyObject *obj)
  This is Unstable API. It may change without warning in minor releases.

  Check if obj is a unique temporary object. Returns `1` if obj is known to be a unique temporary object, and `0` otherwise. This function cannot fail, but the check is conservative, and may return `0` in some cases even if obj is a unique temporary object.

  If an object is a unique temporary, it is guaranteed that the current code has the only reference to the object. For arguments to C functions, this should be used instead of checking if the reference count is `1`. Starting with Python 3.14, the interpreter internally avoids some reference count modifications when loading objects onto the operands stack by borrowing references when possible, which means that a reference count of `1` by itself does not guarantee that a function argument uniquely referenced.

  In the example below, `my_func` is called with a unique temporary object as its argument:

      my_func([1, 2, 3])

  In the example below, `my_func` is not called with a unique temporary object as its argument, even if its refcount is `1`:

      my_list = [1, 2, 3]
      my_func(my_list)

  See also the function `Py_REFCNT()`.

  Added in version 3.14.

int PyUnstable_IsImmortal(PyObject *obj)
  This is Unstable API. It may change without warning in minor releases.

  This function returns non-zero if obj is immortal, and zero otherwise. This function cannot fail.

  Nota

  Objects that are immortal in one CPython version are not guaranteed to be immortal in another.

  Added in version 3.14.

int PyUnstable_TryIncRef(PyObject *obj)
  This is Unstable API. It may change without warning in minor releases.

  Increments the reference count of obj if it is not zero. Returns `1` if the object’s reference count was successfully incremented. Otherwise, this function returns `0`.

  `PyUnstable_EnableTryIncRef()` must have been called earlier on obj or this function may spuriously return `0` in the free-threaded build.

  This function is logically equivalent to the following C code, except that it behaves atomically in the free-threaded build:

      if (Py_REFCNT(op) > 0) {
         Py_INCREF(op);
         return 1;
      }
      return 0;

  This is intended as a building block for managing weak references without the overhead of a Python weak reference object.

  Typically, correct use of this function requires support from obj’s deallocator (`tp_dealloc`). For example, the following sketch could be adapted to implement a «weakmap» that works like a `WeakValueDictionary` for a specific type:

      PyMutex mutex;

      PyObject *
      add_entry(weakmap_key_type *key, PyObject *value)
      {
          PyUnstable_EnableTryIncRef(value);
          weakmap_type weakmap = ...;
          PyMutex_Lock(&mutex);
          weakmap_add_entry(weakmap, key, value);
          PyMutex_Unlock(&mutex);
          Py_RETURN_NONE;
      }

      PyObject *
      get_value(weakmap_key_type *key)
      {
          weakmap_type weakmap = ...;
          PyMutex_Lock(&mutex);
          PyObject *result = weakmap_find(weakmap, key);
          if (PyUnstable_TryIncRef(result)) {
              // `result` is safe to use
              PyMutex_Unlock(&mutex);
              return result;
          }
          // if we get here, `result` is starting to be garbage-collected,
          // but has not been removed from the weakmap yet
          PyMutex_Unlock(&mutex);
          return NULL;
      }

      // tp_dealloc function for weakmap values
      void
      value_dealloc(PyObject *value)
      {
          weakmap_type weakmap = ...;
          PyMutex_Lock(&mutex);
          weakmap_remove_value(weakmap, value);

          ...
          PyMutex_Unlock(&mutex);
      }

  Added in version 3.14.

void PyUnstable_EnableTryIncRef(PyObject *obj)
  This is Unstable API. It may change without warning in minor releases.

  Enables subsequent uses of `PyUnstable_TryIncRef()` on obj. The caller must hold a strong reference to obj when calling this.

  Added in version 3.14.

int PyUnstable_Object_IsUniquelyReferenced(PyObject *op)
  This is Unstable API. It may change without warning in minor releases.

  Determine if op only has one reference.

  On GIL-enabled builds, this function is equivalent to Py_REFCNT(op) == 1.

  On a free-threaded build, this checks if op’s reference count is equal to one and additionally checks if op is only used by this thread. Py_REFCNT(op) == 1 is not thread-safe on free-threaded builds; prefer this function.

  The caller must hold an attached thread state, despite the fact that this function doesn’t call into the Python interpreter. This function cannot fail.

  Added in version 3.14.