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bpo-47220: Document the optional callback parameter of weakref.WeakMethod #25491
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| Original file line number | Diff line number | Diff line change |
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@@ -95,13 +95,13 @@ See :ref:`__slots__ documentation <slots>` for details. | |
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| .. class:: ref(object[, callback]) | ||
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| Return a weak reference to *object*. The original object can be retrieved by | ||
| calling the reference object if the referent is still alive; if the referent is | ||
| no longer alive, calling the reference object will cause :const:`None` to be | ||
| returned. If *callback* is provided and not :const:`None`, and the returned | ||
| weakref object is still alive, the callback will be called when the object is | ||
| about to be finalized; the weak reference object will be passed as the only | ||
| parameter to the callback; the referent will no longer be available. | ||
| Return a weak reference to *object*. The referent can be retrieved by | ||
| calling the weak reference if the referent is still alive; if the referent is | ||
| no longer alive, calling the weak reference will cause :const:`None` to be | ||
| returned. If *callback* is provided and not :const:`None`, and the weak | ||
| reference is still alive, the callback will be called when the referent is | ||
| about to be finalized; the weak reference will be passed as the only | ||
| argument to the callback; the referent will no longer be available. | ||
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| It is allowable for many weak references to be constructed for the same object. | ||
| Callbacks registered for each weak reference will be called from the most | ||
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@@ -117,9 +117,9 @@ See :ref:`__slots__ documentation <slots>` for details. | |
| the call will raise :exc:`TypeError`. | ||
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| Weak references support tests for equality, but not ordering. If the referents | ||
| are still alive, two references have the same equality relationship as their | ||
| are still alive, two weak references have the same equality relationship as their | ||
| referents (regardless of the *callback*). If either referent has been deleted, | ||
| the references are equal only if the reference objects are the same object. | ||
| two weak references are equal only if the weak references are the same object. | ||
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| This is a subclassable type rather than a factory function. | ||
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@@ -137,15 +137,15 @@ See :ref:`__slots__ documentation <slots>` for details. | |
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| Return a proxy to *object* which uses a weak reference. This supports use of | ||
| the proxy in most contexts instead of requiring the explicit dereferencing used | ||
| with weak reference objects. The returned object will have a type of either | ||
| with weak references. The returned object will have a type of either | ||
| ``ProxyType`` or ``CallableProxyType``, depending on whether *object* is | ||
| callable. Proxy objects are not :term:`hashable` regardless of the referent; this | ||
| callable. Proxies are not :term:`hashable` regardless of the referent; this | ||
| avoids a number of problems related to their fundamentally mutable nature, and | ||
| prevent their use as dictionary keys. *callback* is the same as the parameter | ||
| prevents their use as dictionary keys. *callback* is the same as the parameter | ||
| of the same name to the :func:`ref` function. | ||
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| .. versionchanged:: 3.8 | ||
| Extended the operator support on proxy objects to include the matrix | ||
| Extended the operator support on proxies to include the matrix | ||
| multiplication operators ``@`` and ``@=``. | ||
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@@ -156,7 +156,7 @@ See :ref:`__slots__ documentation <slots>` for details. | |
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| .. function:: getweakrefs(object) | ||
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| Return a list of all weak reference and proxy objects which refer to *object*. | ||
| Return a list of all weak references and proxies which refer to *object*. | ||
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| .. class:: WeakKeyDictionary([dict]) | ||
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@@ -171,10 +171,10 @@ See :ref:`__slots__ documentation <slots>` for details. | |
| Added support for ``|`` and ``|=`` operators, specified in :pep:`584`. | ||
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| :class:`WeakKeyDictionary` objects have an additional method that | ||
| exposes the internal references directly. The references are not guaranteed to | ||
| be "live" at the time they are used, so the result of calling the references | ||
| exposes the internal weak references directly. The weak references are not guaranteed to | ||
| be "live" at the time they are used, so the result of calling them | ||
| needs to be checked before being used. This can be used to avoid creating | ||
| references that will cause the garbage collector to keep the keys around longer | ||
| strong references that will cause the garbage collector to keep the keys around longer | ||
| than needed. | ||
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@@ -207,7 +207,7 @@ objects. | |
| discarded when no strong reference to it exists any more. | ||
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| .. class:: WeakMethod(method) | ||
| .. class:: WeakMethod(method[, callback]) | ||
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| A custom :class:`ref` subclass which simulates a weak reference to a bound | ||
| method (i.e., a method defined on a class and looked up on an instance). | ||
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@@ -233,13 +233,15 @@ objects. | |
| >>> r() | ||
| >>> | ||
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| *callback* is the same as the parameter of the same name to the :func:`ref` function. | ||
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| .. versionadded:: 3.4 | ||
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| .. class:: finalize(obj, func, /, *args, **kwargs) | ||
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| Return a callable finalizer object which will be called when *obj* | ||
| is garbage collected. Unlike an ordinary weak reference, a finalizer | ||
| will always survive until the reference object is collected, greatly | ||
| Return a callable finalizer which will be called when *obj* | ||
| is garbage collected. Unlike an ordinary weak reference, a finalizer | ||
| will always survive until the referent is collected, greatly | ||
| simplifying lifecycle management. | ||
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| A finalizer is considered *alive* until it is called (either explicitly | ||
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@@ -292,7 +294,7 @@ objects. | |
| .. note:: | ||
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| It is important to ensure that *func*, *args* and *kwargs* do | ||
| not own any references to *obj*, either directly or indirectly, | ||
| not own any strong references to *obj*, either directly or indirectly, | ||
| since otherwise *obj* will never be garbage collected. In | ||
| particular, *func* should not be a bound method of *obj*. | ||
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@@ -301,17 +303,17 @@ objects. | |
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| .. data:: ReferenceType | ||
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| The type object for weak references objects. | ||
| The type object for weak references. | ||
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| .. data:: ProxyType | ||
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| The type object for proxies of objects which are not callable. | ||
| The type object for proxies to objects which are not callable. | ||
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| .. data:: CallableProxyType | ||
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| The type object for proxies of callable objects. | ||
| The type object for proxies to callable objects. | ||
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| .. data:: ProxyTypes | ||
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@@ -333,8 +335,8 @@ objects. | |
| Weak Reference Objects | ||
| ---------------------- | ||
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| Weak reference objects have no methods and no attributes besides | ||
| :attr:`ref.__callback__`. A weak reference object allows the referent to be | ||
| Weak references have no methods and no attributes besides | ||
| :attr:`ref.__callback__`. A weak reference allows the referent to be | ||
| obtained, if it still exists, by calling it: | ||
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| >>> import weakref | ||
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@@ -347,18 +349,18 @@ obtained, if it still exists, by calling it: | |
| >>> o is o2 | ||
| True | ||
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| If the referent no longer exists, calling the reference object returns | ||
| If the referent no longer exists, calling the weak reference returns | ||
| :const:`None`: | ||
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| >>> del o, o2 | ||
| >>> print(r()) | ||
| None | ||
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| Testing that a weak reference object is still live should be done using the | ||
| Testing that a weak reference is still live should be done using the | ||
| expression ``ref() is not None``. Normally, application code that needs to use | ||
| a reference object should follow this pattern:: | ||
| a weak reference should follow this pattern:: | ||
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| # r is a weak reference object | ||
| # r is a weak reference | ||
| o = r() | ||
| if o is None: | ||
| # referent has been garbage collected | ||
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@@ -375,7 +377,7 @@ applications as well as single-threaded applications. | |
| Specialized versions of :class:`ref` objects can be created through subclassing. | ||
| This is used in the implementation of the :class:`WeakValueDictionary` to reduce | ||
| the memory overhead for each entry in the mapping. This may be most useful to | ||
| associate additional information with a reference, but could also be used to | ||
| associate additional information with a weak reference, but could also be used to | ||
| insert additional processing on calls to retrieve the referent. | ||
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| This example shows how a subclass of :class:`ref` can be used to store | ||
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@@ -393,7 +395,7 @@ the referent is accessed:: | |
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| def __call__(self): | ||
| """Return a pair containing the referent and the number of | ||
| times the reference has been called. | ||
| times the weak reference has been called. | ||
| """ | ||
| ob = super().__call__() | ||
| if ob is not None: | ||
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@@ -435,8 +437,8 @@ Finalizer Objects | |
| ----------------- | ||
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| The main benefit of using :class:`finalize` is that it makes it simple | ||
| to register a callback without needing to preserve the returned finalizer | ||
| object. For instance | ||
| to register a callback without needing to preserve the returned finalizer. | ||
| For instance | ||
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| >>> import weakref | ||
| >>> class Object: | ||
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@@ -492,7 +494,7 @@ is still alive. For instance | |
| obj dead or exiting | ||
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| Comparing finalizers with :meth:`__del__` methods | ||
| Comparing Finalizers with :meth:`__del__` Methods | ||
| ------------------------------------------------- | ||
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| Suppose we want to create a class whose instances represent temporary | ||
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@@ -531,7 +533,7 @@ However, handling of :meth:`__del__` methods is notoriously implementation | |
| specific, since it depends on internal details of the interpreter's garbage | ||
| collector implementation. | ||
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| A more robust alternative can be to define a finalizer which only references | ||
| A more robust alternative can be used to define a finalizer which only references | ||
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| the specific functions and objects that it needs, rather than having access | ||
| to the full state of the object:: | ||
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@@ -551,8 +553,8 @@ Defined like this, our finalizer only receives a reference to the details | |
| it needs to clean up the directory appropriately. If the object never gets | ||
| garbage collected the finalizer will still be called at exit. | ||
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| The other advantage of weakref based finalizers is that they can be used to | ||
| register finalizers for classes where the definition is controlled by a | ||
| The other advantage of finalizers is that they can be used | ||
| for classes where the definition is controlled by a | ||
| third party, such as running code when a module is unloaded:: | ||
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| import weakref, sys | ||
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@@ -563,7 +565,7 @@ third party, such as running code when a module is unloaded:: | |
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| .. note:: | ||
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| If you create a finalizer object in a daemonic thread just as the program | ||
| If you create a finalizer in a daemonic thread just as the program | ||
| exits then there is the possibility that the finalizer | ||
| does not get called at exit. However, in a daemonic thread | ||
| :func:`atexit.register`, ``try: ... finally: ...`` and ``with: ...`` | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,2 @@ | ||
| Document the optional *callback* parameter of :class:`WeakMethod`. Patch by | ||
| Géry Ogam. |
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