# Contagem de referências

As funções e macros nesta sessão são usadas para o gerenciamento de contagem de referências de objetos Python.

Py_ssize_t Py_REFCNT(PyObject *o)

  Obtêm a contagem de referências do objeto Python o.

  Note that the returned value may not actually reflect how many references to the object are actually held. For example, some objects are “immortal” and have a very high refcount that does not reflect the actual number of references. Consequently, do not rely on the returned value to be accurate, other than a value of 0 or 1.

  Use a função `Py_SET_REFCNT()` para definir uma contagem de referências de um objeto.

  Alterado na versão 3.10: `Py_REFCNT()` is changed to the inline static function.

  Alterado na versão 3.11: The parameter type is no longer const PyObject*.

void Py_SET_REFCNT(PyObject *o, Py_ssize_t refcnt)

  Set the object o reference counter to refcnt.

  Note that this function has no effect on immortal objects.

  Adicionado na versão 3.9.

  Alterado na versão 3.12: Os objetos imortais não são modificados.

void Py_INCREF(PyObject *o)

  Indicate taking a new strong reference to object o, indicating it is in use and should not be destroyed.

  Esta função é geralmente usada para transformar uma referência emprestada em uma referência forte local. A função `Py_NewRef()` pode ser usada para criar uma nova referência forte.

  When done using the object, release it by calling `Py_DECREF()`.

  The object must not be `NULL`; if you aren’t sure that it isn’t `NULL`, use `Py_XINCREF()`.

  Do not expect this function to actually modify o in any way. For at least some objects, this function has no effect.

  Alterado na versão 3.12: Os objetos imortais não são modificados.

void Py_XINCREF(PyObject *o)

  Semelhante a `Py_INCREF()`, mas o objeto o pode ser `NULL`, caso em que isso não tem efeito.

  Veja também `Py_XNewRef()`.

PyObject *Py_NewRef(PyObject *o)
  Parte da ABI Estável desde a versão 3.10.

  Create a new strong reference to an object: call `Py_INCREF()` on o and return the object o.

  When the strong reference is no longer needed, `Py_DECREF()` should be called on it to release the reference.

  The object o must not be `NULL`; use `Py_XNewRef()` if o can be `NULL`.

  Por exemplo:

      Py_INCREF(obj);
      self->attr = obj;

  can be written as:

      self->attr = Py_NewRef(obj);

  See also `Py_INCREF()`.

  Adicionado na versão 3.10.

PyObject *Py_XNewRef(PyObject *o)
  Parte da ABI Estável desde a versão 3.10.

  Semelhante a `Py_NewRef()`, mas o objeto o pode ser NULL.

  Se o objeto o é `NULL`, a função apenas retorna `NULL`.

  Adicionado na versão 3.10.

void Py_DECREF(PyObject *o)

  Release a strong reference to object o, indicating the reference is no longer used.

  Once the last strong reference is released (i.e. the object’s reference count reaches 0), the object’s type’s deallocation function (which must not be `NULL`) is invoked.

  This function is usually used to delete a strong reference before exiting its scope.

  The object must not be `NULL`; if you aren’t sure that it isn’t `NULL`, use `Py_XDECREF()`.

  Do not expect this function to actually modify o in any way. For at least some objects, this function has no effect.

  Aviso

  The deallocation function can cause arbitrary Python code to be invoked (e.g. when a class instance with a `__del__()` method is deallocated). While exceptions in such code are not propagated, the executed code has free access to all Python global variables. This means that any object that is reachable from a global variable should be in a consistent state before `Py_DECREF()` is invoked. For example, code to delete an object from a list should copy a reference to the deleted object in a temporary variable, update the list data structure, and then call `Py_DECREF()` for the temporary variable.

  Alterado na versão 3.12: Os objetos imortais não são modificados.

void Py_XDECREF(PyObject *o)

  Similar to `Py_DECREF()`, but the object o can be `NULL`, in which case this has no effect. The same warning from `Py_DECREF()` applies here as well.

void Py_CLEAR(PyObject *o)

  Release a strong reference for object o. The object may be `NULL`, in which case the macro has no effect; otherwise the effect is the same as for `Py_DECREF()`, except that the argument is also set to `NULL`. The warning for `Py_DECREF()` does not apply with respect to the object passed because the macro carefully uses a temporary variable and sets the argument to `NULL` before releasing the reference.

  It is a good idea to use this macro whenever releasing a reference to an object that might be traversed during garbage collection.

  Alterado na versão 3.12: The macro argument is now only evaluated once. If the argument has side effects, these are no longer duplicated.

void Py_IncRef(PyObject *o)
  Parte da ABI Estável.

  Indicate taking a new strong reference to object o. A function version of `Py_XINCREF()`. It can be used for runtime dynamic embedding of Python.

void Py_DecRef(PyObject *o)
  Parte da ABI Estável.

  Release a strong reference to object o. A function version of `Py_XDECREF()`. It can be used for runtime dynamic embedding of Python.

Py_SETREF(dst, src)

  Macro safely releasing a strong reference to object dst and setting dst to src.

  As in case of `Py_CLEAR()`, “the obvious” code can be deadly:

      Py_DECREF(dst);
      dst = src;

  The safe way is:

      Py_SETREF(dst, src);

  That arranges to set dst to src _before_ releasing the reference to the old value of dst, so that any code triggered as a side-effect of dst getting torn down no longer believes dst points to a valid object.

  Adicionado na versão 3.6.

  Alterado na versão 3.12: The macro arguments are now only evaluated once. If an argument has side effects, these are no longer duplicated.

Py_XSETREF(dst, src)

  Variant of `Py_SETREF` macro that uses `Py_XDECREF()` instead of `Py_DECREF()`.

  Adicionado na versão 3.6.

  Alterado na versão 3.12: The macro arguments are now only evaluated once. If an argument has side effects, these are no longer duplicated.