# Object Protocol

PyObject *Py_GetConstant(unsigned int constant_id)
  Parte del ABI Stabile dalla versione 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.

  Dettaglio dell’implementazione di CPython: In CPython, all of these constants are immortal.

PyObject *Py_GetConstantBorrowed(unsigned int constant_id)
  Parte del ABI Stabile dalla versione 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

  The `NotImplemented` singleton, used to signal that an operation is not implemented for the given type combination.

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()`.

void PyObject_Dump(PyObject *op)

  Dump an object op to `stderr`. This should only be used for debugging.

  The output is intended to try dumping objects even after memory corruption:

  - Information is written starting with fields that are the least likely to crash when accessed.

  - This function can be called without an attached thread state, but it’s not recommended to do so: it can cause deadlocks.

  - An object that does not belong to the current interpreter may be dumped, but this may also cause crashes or unintended behavior.

  - Implement a heuristic to detect if the object memory has been freed. Don’t display the object contents in this case, only its memory address.

  - The output format may change at any time.

  Example of output:

      object address  : 0x7f80124702c0
      object refcount : 2
      object type     : 0x9902e0
      object type name: str
      object repr     : 'abcdef'

  Added in version 3.15.

int PyObject_HasAttrWithError(PyObject *o, PyObject *attr_name)
  Parte del ABI Stabile dalla versione 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)
  Parte del ABI Stabile dalla versione 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)
  Parte del ABI Stabile.

  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)
  Parte del ABI Stabile.

  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)
  Valore di ritorno: Nuovo riferimento. Parte del ABI Stabile.

  Retrieve an attribute named attr_name from object o. Returns the attribute value on success, or `NULL` on failure. This is the equivalent of the Python expression `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)
  Valore di ritorno: Nuovo riferimento. Parte del ABI Stabile.

  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);
  Parte del ABI Stabile dalla versione 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);
  Parte del ABI Stabile dalla versione 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)
  Valore di ritorno: Nuovo riferimento. Parte del ABI Stabile.

  Generic attribute getter function that is meant to be put into a type object’s `tp_getattro` slot. It looks for a descriptor in the dictionary of classes in the object’s MRO as well as an attribute in the object’s `__dict__` (if present). As outlined in Implementing Descriptors, data descriptors take preference over instance attributes, while non-data descriptors don’t. Otherwise, an `AttributeError` is raised.

int PyObject_SetAttr(PyObject *o, PyObject *attr_name, PyObject *v)
  Parte del ABI Stabile.

  Set the value of the attribute named attr_name, for object o, to the value v. Raise an exception and return `-1` on failure; return `0` on success. This is the equivalent of the Python statement `o.attr_name = v`.

  If v is `NULL`, the attribute is deleted. This behaviour is deprecated in favour of using `PyObject_DelAttr()`, but there are currently no plans to remove it.

  The function must not be called with a `NULL` v and an exception set. This case can arise from forgetting `NULL` checks and would delete the attribute.

  Cambiato nella versione 3.15: Must not be called with NULL value if an exception is set.

int PyObject_SetAttrString(PyObject *o, const char *attr_name, PyObject *v)
  Parte del ABI Stabile.

  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*.

  If v is `NULL`, the attribute is deleted, but this feature is deprecated in favour of using `PyObject_DelAttrString()`.

  The function must not be called with a `NULL` v and an exception set. This case can arise from forgetting `NULL` checks and would delete the attribute.

  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.

  Cambiato nella versione 3.15: Must not be called with NULL value if an exception is set.

int PyObject_GenericSetAttr(PyObject *o, PyObject *name, PyObject *value)
  Parte del ABI Stabile.

  Generic attribute setter and deleter function that is meant to be put into a type object’s `tp_setattro` slot. It looks for a data descriptor in the dictionary of classes in the object’s MRO, and if found it takes preference over setting or deleting the attribute in the instance dictionary. Otherwise, the attribute is set or deleted in the object’s `__dict__` (if present). On success, `0` is returned, otherwise an `AttributeError` is raised and `-1` is returned.

int PyObject_DelAttr(PyObject *o, PyObject *attr_name)
  Parte del ABI Stabile dalla versione 3.13.

  Delete attribute named attr_name, for object o. Returns `-1` on failure. This is the equivalent of the Python statement `del o.attr_name`.

int PyObject_DelAttrString(PyObject *o, const char *attr_name)
  Parte del ABI Stabile dalla versione 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)
  Valore di ritorno: Nuovo riferimento. Parte del ABI Stabile dalla versione 3.10.

  A generic implementation for the getter of a `__dict__` descriptor. It creates the dictionary if necessary.

  This function may also be called to get the `__dict__` of the object o. Pass `NULL` for context when calling it. Since this function may need to allocate memory for the dictionary, it may be more efficient to call `PyObject_GetAttr()` when accessing an attribute on the object.

  On failure, returns `NULL` with an exception set.

  Added in version 3.3.

int PyObject_GenericSetDict(PyObject *o, PyObject *value, void *context)
  Parte del ABI Stabile dalla versione 3.7.

  A generic implementation for the setter of a `__dict__` descriptor. This implementation does not allow the dictionary to be deleted.

  Added in version 3.3.

PyObject **_PyObject_GetDictPtr(PyObject *obj)

  Return a pointer to `__dict__` of the object obj. If there is no `__dict__`, return `NULL` without setting an exception.

  This function may need to allocate memory for the dictionary, so it may be more efficient to call `PyObject_GetAttr()` when accessing an attribute on the object.

PyObject *PyObject_RichCompare(PyObject *o1, PyObject *o2, int opid)
  Valore di ritorno: Nuovo riferimento. Parte del ABI Stabile.

  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)
  Parte del ABI Stabile.

  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)
  Parte del ABI Stabile.

  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)
  Valore di ritorno: Nuovo riferimento. Parte del ABI Stabile.

  Compute a string representation of object o. Returns the string representation on success, `NULL` on failure. This is the equivalent of the Python expression `repr(o)`. Called by the `repr()` built-in function.

  Cambiato nella versione 3.4: This function now includes a debug assertion to help ensure that it does not silently discard an active exception.

PyObject *PyObject_ASCII(PyObject *o)
  Valore di ritorno: Nuovo riferimento. Parte del ABI Stabile.

  As `PyObject_Repr()`, compute a string representation of object o, but escape the non-ASCII characters in the string returned by `PyObject_Repr()` with `\x`, `\u` or `\U` escapes. This generates a string similar to that returned by `PyObject_Repr()` in Python 2. Called by the `ascii()` built-in function.

PyObject *PyObject_Str(PyObject *o)
  Valore di ritorno: Nuovo riferimento. Parte del ABI Stabile.

  Compute a string representation of object o. Returns the string representation on success, `NULL` on failure. This is the equivalent of the Python expression `str(o)`. Called by the `str()` built-in function and, therefore, by the `print()` function.

  Cambiato nella versione 3.4: This function now includes a debug assertion to help ensure that it does not silently discard an active exception.

PyObject *PyObject_Bytes(PyObject *o)
  Valore di ritorno: Nuovo riferimento. Parte del ABI Stabile.

  Compute a bytes representation of object o. `NULL` is returned on failure and a bytes object on success. This is equivalent to the Python expression `bytes(o)`, when o is not an integer. Unlike `bytes(o)`, a TypeError is raised when o is an integer instead of a zero-initialized bytes object.

int PyObject_IsSubclass(PyObject *derived, PyObject *cls)
  Parte del ABI Stabile.

  Return `1` if the class derived is identical to or derived from the class cls, otherwise return `0`. In case of an error, return `-1`.

  If cls is a tuple, the check will be done against every entry in cls. The result will be `1` when at least one of the checks returns `1`, otherwise it will be `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)
  Parte del ABI Stabile.

  Return `1` if inst is an instance of the class cls or a subclass of cls, or `0` if not. On error, returns `-1` and sets an exception.

  If cls is a tuple, the check will be done against every entry in cls. The result will be `1` when at least one of the checks returns `1`, otherwise it will be `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)
  Parte del ABI Stabile.

  Compute and return the hash value of an object o. On failure, return `-1`. This is the equivalent of the Python expression `hash(o)`.

  Cambiato nella versione 3.2: The return type is now Py_hash_t. This is a signed integer the same size as `Py_ssize_t`.

Py_hash_t PyObject_HashNotImplemented(PyObject *o)
  Parte del ABI Stabile.

  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)
  Parte del ABI Stabile.

  Returns `1` if the object o is considered to be true, and `0` otherwise. This is equivalent to the Python expression `not not o`. On failure, return `-1`.

int PyObject_Not(PyObject *o)
  Parte del ABI Stabile.

  Returns `0` if the object o is considered to be true, and `1` otherwise. This is equivalent to the Python expression `not o`. On failure, return `-1`.

PyObject *PyObject_Type(PyObject *o)
  Valore di ritorno: Nuovo riferimento. Parte del ABI Stabile.

  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)

  Return non-zero if the object o is of type type or a subtype of type, and `0` otherwise. Both parameters must be non-`NULL`.

Py_ssize_t PyObject_Size(PyObject *o)
Py_ssize_t PyObject_Length(PyObject *o)
  Parte del ABI Stabile.

  Return the length of object o. If the object o provides either the sequence and mapping protocols, the sequence length is returned. On error, `-1` is returned. This is the equivalent to the Python expression `len(o)`.

Py_ssize_t PyObject_LengthHint(PyObject *o, Py_ssize_t defaultvalue)

  Return an estimated length for the object o. First try to return its actual length, then an estimate using `__length_hint__()`, and finally return the default value. On error return `-1`. This is the equivalent to the Python expression `operator.length_hint(o, defaultvalue)`.

  Added in version 3.4.

PyObject *PyObject_GetItem(PyObject *o, PyObject *key)
  Valore di ritorno: Nuovo riferimento. Parte del ABI Stabile.

  Return element of o corresponding to the object key or `NULL` on failure. This is the equivalent of the Python expression `o[key]`.

int PyObject_SetItem(PyObject *o, PyObject *key, PyObject *v)
  Parte del ABI Stabile.

  Map the object key to the value v. Raise an exception and return `-1` on failure; return `0` on success. This is the equivalent of the Python statement `o[key] = v`. This function does not steal a reference to v.

int PyObject_DelItem(PyObject *o, PyObject *key)
  Parte del ABI Stabile.

  Remove the mapping for the object key from the object o. Return `-1` on failure. This is equivalent to the Python statement `del o[key]`.

int PyObject_DelItemString(PyObject *o, const char *key)
  Parte del ABI Stabile.

  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)
  Valore di ritorno: Nuovo riferimento. Parte del ABI Stabile.

  This is equivalent to the Python expression `dir(o)`, returning a (possibly empty) list of strings appropriate for the object argument, or `NULL` if there was an error. If the argument is `NULL`, this is like the Python `dir()`, returning the names of the current locals; in this case, if no execution frame is active then `NULL` is returned but `PyErr_Occurred()` will return false.

PyObject *PyObject_GetIter(PyObject *o)
  Valore di ritorno: Nuovo riferimento. Parte del ABI Stabile.

  This is equivalent to the Python expression `iter(o)`. It returns a new iterator for the object argument, or the object itself if the object is already an iterator. Raises `TypeError` and returns `NULL` if the object cannot be iterated.

PyObject *PyObject_SelfIter(PyObject *obj)
  Valore di ritorno: Nuovo riferimento. Parte del ABI Stabile.

  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)
  Valore di ritorno: Nuovo riferimento. Parte del ABI Stabile dalla versione 3.10.

  This is the equivalent to the Python expression `aiter(o)`. Takes an `AsyncIterable` object and returns an `AsyncIterator` for it. This is typically a new iterator but if the argument is an `AsyncIterator`, this returns itself. Raises `TypeError` and returns `NULL` if the object cannot be iterated.

  Added in version 3.10.

void *PyObject_GetTypeData(PyObject *o, PyTypeObject *cls)
  Parte del ABI Stabile dalla versione 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)
  Parte del ABI Stabile dalla versione 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)
  Questa pagina API Instabile. Potrebbe cambiare senza preavviso nelle release minori.

  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)
  Questa pagina API Instabile. Potrebbe cambiare senza preavviso nelle release minori.

  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)
  Questa pagina API Instabile. Potrebbe cambiare senza preavviso nelle release minori.

  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)
  Questa pagina API Instabile. Potrebbe cambiare senza preavviso nelle release minori.

  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)
  Questa pagina API Instabile. Potrebbe cambiare senza preavviso nelle release minori.

  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)
  Questa pagina API Instabile. Potrebbe cambiare senza preavviso nelle release minori.

  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.