弱引用對(duì)象

python 支持 “弱引用” 作為一類對(duì)象。具體來(lái)說(shuō)，有兩種直接實(shí)現(xiàn)弱引用的對(duì)象。第一種就是簡(jiǎn)單的引用對(duì)象，第二種盡可能地作用為一個(gè)原對(duì)象的代理。

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int PyWeakref_Check(ob)

如果 ob 是一個(gè)引用或代理對(duì)象則返回真值。 此函數(shù)總是會(huì)成功執(zhí)行。

int PyWeakref_CheckRef(ob)

如果 ob 是一個(gè)引用對(duì)象則返回真值。 此函數(shù)總是會(huì)成功執(zhí)行。

int PyWeakref_CheckProxy(ob)

如果 ob 是一個(gè)代理對(duì)象則返回真值。 此函數(shù)總是會(huì)成功執(zhí)行。

PyObject *PyWeakref_NewRef(PyObject *ob, PyObject *callback)

Return value: New reference. Part of the Stable ABI.

Return a weak reference object for the object ob. This will always return a new reference, but is not guaranteed to create a new object; an existing reference object may be returned. The second parameter, callback, can be a callable object that receives notification when ob is garbage collected; it should accept a single parameter, which will be the weak reference object itself. callback may also be None or NULL. If ob is not a weakly referencable object, or if callback is not callable, None, or NULL, this will return NULL and raise TypeError.

PyObject *PyWeakref_NewProxy(PyObject *ob, PyObject *callback)

Return value: New reference. Part of the Stable ABI.

Return a weak reference proxy object for the object ob. This will always return a new reference, but is not guaranteed to create a new object; an existing proxy object may be returned. The second parameter, callback, can be a callable object that receives notification when ob is garbage collected; it should accept a single parameter, which will be the weak reference object itself. callback may also be None or NULL. If ob is not a weakly referencable object, or if callback is not callable, None, or NULL, this will return NULL and raise TypeError.

PyObject *PyWeakref_GetObject(PyObject *ref)

Return value: Borrowed reference. Part of the Stable ABI.

返回弱引用對(duì)象 ref 的被引用對(duì)象。如果被引用對(duì)象不再存在，則返回 Py_None。

備注

該函數(shù)返回被引用對(duì)象的一個(gè) borrowed reference。 這意味著應(yīng)該總是在該對(duì)象上調(diào)用 Py_INCREF()，除非是當(dāng)它在借入引用的最后一次被使用之前無(wú)法被銷毀的時(shí)候。

PyObject *PyWeakref_GET_OBJECT(PyObject *ref)

Return value: Borrowed reference.

Similar to PyWeakref_GetObject(), but does no error checking.

當(dāng)前題目：創(chuàng)新互聯(lián)Python教程：弱引用對(duì)象
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