Contagem de Referências¶
The functions and macros in this section are used for managing reference counts of Python objects.
-
Py_ssize_t Py_REFCNT(PyObject *o)¶
- Parte da ABI Estável desde a versão 3.14.
Get the reference count of the Python object o.
Observe que o valor retornado pode não refletir realmente quantas referências ao objeto são realmente mantidas. Por exemplo, alguns objetos são imortais e têm uma refcount muito alta que não reflete o número real de referências. Consequentemente, não confie no valor retornado para ser preciso, exceto um valor de 0 ou 1.
Use the
Py_SET_REFCNT()
function to set an object reference count.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.
Em uma construção do Python com threads threads livres, se refcnt for maior que
UINT32_MAX
, o objeto será transformado em imortal.This function has no effect on immortal objects.
Adicionado na versão 3.9.
Alterado na versão 3.12: Immortal objects are not modified.
-
void Py_INCREF(PyObject *o)¶
Indicate taking a new strong reference to object o, indicating it is in use and should not be destroyed.
This function has no effect on immortal objects.
This function is usually used to convert a borrowed reference to a strong reference in-place. The
Py_NewRef()
function can be used to create a new strong reference.When done using the object, release is by calling
Py_DECREF()
.The object must not be
NULL
; if you aren’t sure that it isn’tNULL
, usePy_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: Immortal objects are not modified.
-
void Py_XINCREF(PyObject *o)¶
Similar to
Py_INCREF()
, but the object o can beNULL
, in which case this has no effect.See also
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
; usePy_XNewRef()
if o can beNULL
.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.
Similar to
Py_NewRef()
, but the object o can be NULL.If the object o is
NULL
, the function just returnsNULL
.Adicionado na versão 3.10.
-
void Py_DECREF(PyObject *o)¶
Release a strong reference to object o, indicating the reference is no longer used.
This function has no effect on immortal objects.
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’tNULL
, usePy_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 beforePy_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 callPy_DECREF()
for the temporary variable.Alterado na versão 3.12: Immortal objects are not modified.
-
void Py_XDECREF(PyObject *o)¶
Similar to
Py_DECREF()
, but the object o can beNULL
, in which case this has no effect. The same warning fromPy_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 forPy_DECREF()
, except that the argument is also set toNULL
. The warning forPy_DECREF()
does not apply with respect to the object passed because the macro carefully uses a temporary variable and sets the argument toNULL
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 usesPy_XDECREF()
instead ofPy_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.