The functions and macros in this section are used for managing reference counts of Python objects.
Py_REFCNT(
*o)
Part of the
since version 3.14.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
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
function to set an object reference count.
Changed in version 3.10:
is changed to the inline static function.
Changed in version 3.11: The parameter type is no longer const
*.
voidPy_SET_REFCNT(
*o,
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
.
This function has no effect on
objects.
Added in version 3.9.
Changed in version 3.12: Immortal objects are not modified.
voidPy_INCREF(
*o)
Indicate taking a new
to object o, indicating it is in use and should not be destroyed.
This function has no effect on
objects.
This function is usually used to convert a
to a
in-place. The
function can be used to create a new strong reference.
When done using the object, release is by calling
.
The object must not be NULL; if you aren’t sure that it isn’t NULL, use
.
Do not expect this function to actually modify o in any way. For at least
, this function has no effect.
Changed in version 3.12: Immortal objects are not modified.
voidPy_XINCREF(
*o)
Similar to
, but the object o can be NULL, in which case this has no effect.
See also
.
*Py_NewRef(
*o)
Part of the
since version 3.10.Create a new
to an object: call
on o and return the object o.
When the
is no longer needed,
should be called on it to release the reference.
The object o must not be NULL; use
if o can be NULL.
For example:
Py_INCREF(obj);self->attr=obj;can be written as:
self->attr=Py_NewRef(obj);See also
.
Added in version 3.10.
*Py_XNewRef(
*o)
Part of the
since version 3.10.Similar to
, but the object o can be NULL.
If the object o is NULL, the function just returns NULL.
Added in version 3.10.
voidPy_DECREF(
*o)
Release a
to object o, indicating the reference is no longer used.
This function has no effect on
objects.
Once the last
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
before exiting its scope.
The object must not be NULL; if you aren’t sure that it isn’t NULL, use
.
Do not expect this function to actually modify o in any way. For at least
, this function has no effect.
Warning
The deallocation function can cause arbitrary Python code to be invoked (e.g. when a class instance with a
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
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.
Changed in version 3.12: Immortal objects are not modified.
voidPy_XDECREF(
*o)
Similar to
, but the object o can be NULL, in which case this has no effect. The same warning from Py_DECREF() applies here as well.
voidPy_CLEAR(
*o)
Release a
for object o. The object may be NULL, in which case the macro has no effect; otherwise the effect is the same as for
, 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.
Changed in version 3.12: The macro argument is now only evaluated once. If the argument has side effects, these are no longer duplicated.
voidPy_IncRef(
*o)
Part of the
.Indicate taking a new
to object o. A function version of
. It can be used for runtime dynamic embedding of Python.
voidPy_DecRef(
*o)
Part of the
.Release a
to object o. A function version of
. It can be used for runtime dynamic embedding of Python.
Py_SETREF(dst, src)
Macro safely releasing a
to object dst and setting dst to src.
As in case of
, “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 srcbefore 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.
Added in version 3.6.
Changed in 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
macro that uses
instead of
.
Added in version 3.6.
Changed in version 3.12: The macro arguments are now only evaluated once. If an argument has side effects, these are no longer duplicated.