mirror of https://github.com/python/cpython
63 lines
2.3 KiB
ReStructuredText
63 lines
2.3 KiB
ReStructuredText
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.. highlightlang:: c
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.. _weakrefobjects:
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Weak Reference Objects
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----------------------
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Python supports *weak references* as first-class objects. There are two
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specific object types which directly implement weak references. The first is a
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simple reference object, and the second acts as a proxy for the original object
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as much as it can.
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.. cfunction:: int PyWeakref_Check(ob)
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Return true if *ob* is either a reference or proxy object.
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.. cfunction:: int PyWeakref_CheckRef(ob)
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Return true if *ob* is a reference object.
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.. cfunction:: int PyWeakref_CheckProxy(ob)
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Return true if *ob* is a proxy object.
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.. cfunction:: PyObject* PyWeakref_NewRef(PyObject *ob, PyObject *callback)
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Return a weak reference object for the object *ob*. This will always return
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a new reference, but is not guaranteed to create a new object; an existing
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reference object may be returned. The second parameter, *callback*, can be a
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callable object that receives notification when *ob* is garbage collected; it
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should accept a single parameter, which will be the weak reference object
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itself. *callback* may also be ``None`` or *NULL*. If *ob* is not a
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weakly-referencable object, or if *callback* is not callable, ``None``, or
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*NULL*, this will return *NULL* and raise :exc:`TypeError`.
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.. cfunction:: PyObject* PyWeakref_NewProxy(PyObject *ob, PyObject *callback)
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Return a weak reference proxy object for the object *ob*. This will always
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return a new reference, but is not guaranteed to create a new object; an
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existing proxy object may be returned. The second parameter, *callback*, can
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be a callable object that receives notification when *ob* is garbage
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collected; it should accept a single parameter, which will be the weak
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reference object itself. *callback* may also be ``None`` or *NULL*. If *ob*
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is not a weakly-referencable object, or if *callback* is not callable,
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``None``, or *NULL*, this will return *NULL* and raise :exc:`TypeError`.
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.. cfunction:: PyObject* PyWeakref_GetObject(PyObject *ref)
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Return the referenced object from a weak reference, *ref*. If the referent is
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no longer live, returns ``None``.
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.. cfunction:: PyObject* PyWeakref_GET_OBJECT(PyObject *ref)
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Similar to :cfunc:`PyWeakref_GetObject`, but implemented as a macro that does no
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error checking.
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