Reference Counting¶
The functions and macros in this section are used for managing reference counts of Python objects.
-
Py_ssize_t Py_REFCNT(PyObject *o)¶
Get the reference count of the Python object 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 the
Py_SET_REFCNT()
function to set an object reference count.Modifié dans la version 3.10:
Py_REFCNT()
is changed to the inline static function.Modifié dans la version 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.
On Python build with Free Threading, if refcnt is larger than
UINT32_MAX
, the object is made immortal.This function has no effect on immortal objects.
Ajouté dans la version 3.9.
Modifié dans la version 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.
Cette fonction est souvent utilisée pour convertir une référence empruntée en une référence forte sur place. La fonction
Py_NewRef()
peut être utilisée pour créer une nouvelle référence forte.When done using the object, release is by calling
Py_DECREF()
.L'objet ne doit pas être
NULL
, la fonctionPy_XINCREF()
doit être utilisée s'il est possible qu'il soitNULL
.Do not expect this function to actually modify o in any way. For at least some objects, this function has no effect.
Modifié dans la version 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.Voir aussi
Py_XNewRef()
.
-
PyObject *Py_NewRef(PyObject *o)¶
- Part of the Stable ABI Depuis la version 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.L'objet o ne doit pas être
NULL
et la fonctionPy_XNewRef()
doit être utilisée si o peut êtreNULL
.Par exemple :
Py_INCREF(obj); self->attr = obj;
peut s'écrire :
self->attr = Py_NewRef(obj);
Voir aussi
Py_INCREF()
.Ajouté dans la version 3.10.
-
PyObject *Py_XNewRef(PyObject *o)¶
- Part of the Stable ABI Depuis la version 3.10.
Semblable à
Py_NewRef()
mais l'objet o peut êtreNULL
.Cette fonction renvoie
NULL
si l'objet o estNULL
.Ajouté dans la version 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.Cette fonction est généralement utilisée pour supprimer une référence forte avant qu'elle ne soit plus accessible.
L'objet en argument ne doit pas être
NULL
.Py_XDECREF()
doit être utilisée si l'objet peut êtreNULL
.Do not expect this function to actually modify o in any way. For at least some objects, this function has no effect.
Avertissement
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.Modifié dans la version 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.
Modifié dans la version 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)¶
- Part of the Stable ABI.
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)¶
- Part of the Stable ABI.
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.
Ajouté dans la version 3.6.
Modifié dans la version 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()
.Ajouté dans la version 3.6.
Modifié dans la version 3.12: The macro arguments are now only evaluated once. If an argument has side effects, these are no longer duplicated.