引用计数 ¶

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.

使用 Py_SET_REFCNT() function to set an object reference count.

3.10 版改变： Py_REFCNT() is changed to the inline static function.

3.11 版改变： The parameter type is no longer const PyObject * .

void Py_SET_REFCNT ( PyObject * o , Py_ssize_t refcnt ) ¶

设置对象 o reference counter to refcnt .

On Python build with Free Threading ，若 refcnt > UINT32_MAX , the object is made immortal .

This function has no effect on immortal 对象。

Added in version 3.9.

3.12 版改变： Immortal objects are not modified.

void Py_INCREF ( PyObject * o ) ¶

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

This function has no effect on immortal 对象。

This function is usually used to convert a 借位引用到强引用 in-place. The Py_NewRef() function can be used to create a new 强引用 .

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’t NULL ，使用 Py_XINCREF() .

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

3.12 版改变： Immortal objects are not modified.

void Py_XINCREF ( PyObject * o ) ¶

类似于 Py_INCREF() , but the object o 可以是 NULL , in which case this has no effect.

另请参阅 Py_XNewRef() .

PyObject * Py_NewRef ( PyObject * o ) ¶

属于稳定 ABI (应用程序二进制接口) since version 3.10.

创建新的强引用 to an object: call Py_INCREF() on o and return the object o .

当强引用 is no longer needed, Py_DECREF() should be called on it to release the reference.

The object o 不得为 NULL ；使用 Py_XNewRef() if o 可以是 NULL .

例如：

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

can be written as:

self->attr = Py_NewRef(obj);

另请参阅 Py_INCREF() .

3.10 版添加。

PyObject * Py_XNewRef ( PyObject * o ) ¶

属于稳定 ABI (应用程序二进制接口) since version 3.10.

类似于 Py_NewRef() , but the object o can be NULL.

If the object o is NULL , the function just returns NULL .

3.10 版添加。

void Py_DECREF ( PyObject * o ) ¶

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

This function has no effect on immortal 对象。

Once the last 强引用 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 强引用 before exiting its scope.

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

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

警告

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.

3.12 版改变： Immortal objects are not modified.

void Py_XDECREF ( PyObject * o ) ¶: 类似于 Py_DECREF() , but the object o 可以是 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 强引用 for object o 。对象可能是 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.

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

void Py_IncRef ( PyObject * o ) ¶: 属于稳定 ABI (应用程序二进制接口) .
Indicate taking a new 强引用 to object o . A function version of Py_XINCREF() . It can be used for runtime dynamic embedding of Python.

void Py_DecRef ( PyObject * o ) ¶: 属于稳定 ABI (应用程序二进制接口) .
Release a 强引用 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 强引用 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.

Added in version 3.6.

3.12 版改变： 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() 而不是 Py_DECREF() .

Added in version 3.6.

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

引用计数 ¶

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