diff options
Diffstat (limited to 'Doc/library/weakref.rst')
| -rw-r--r-- | Doc/library/weakref.rst | 32 |
1 files changed, 16 insertions, 16 deletions
diff --git a/Doc/library/weakref.rst b/Doc/library/weakref.rst index 9a1e076..fdfbae0 100644 --- a/Doc/library/weakref.rst +++ b/Doc/library/weakref.rst @@ -20,22 +20,22 @@ In the following, the term :dfn:`referent` means the object which is referred to by a weak reference. A weak reference to an object is not enough to keep the object alive: when the -only remaining references to a referent are weak references, garbage collection -is free to destroy the referent and reuse its memory for something else. A -primary use for weak references is to implement caches or mappings holding large -objects, where it's desired that a large object not be kept alive solely because -it appears in a cache or mapping. For example, if you have a number of large -binary image objects, you may wish to associate a name with each. If you used a -Python dictionary to map names to images, or images to names, the image objects -would remain alive just because they appeared as values or keys in the -dictionaries. The :class:`WeakKeyDictionary`, :class:`WeakValueDictionary` -and :class:`WeakSet` classes supplied by the :mod:`weakref` module are an -alternative, using weak references to construct mappings that don't keep objects -alive solely because they appear in the container objects. -If, for example, an image object is a value in a :class:`WeakValueDictionary`, -then when the last remaining references to that image object are the weak -references held by weak mappings, garbage collection can reclaim the object, -and its corresponding entries in weak mappings are simply deleted. +only remaining references to a referent are weak references, +:term:`garbage collection` is free to destroy the referent and reuse its memory +for something else. A primary use for weak references is to implement caches or +mappings holding large objects, where it's desired that a large object not be +kept alive solely because it appears in a cache or mapping. For example, if you +have a number of large binary image objects, you may wish to associate a name +with each. If you used a Python dictionary to map names to images, or images to +names, the image objects would remain alive just because they appeared as values +or keys in the dictionaries. The :class:`WeakKeyDictionary` and +:class:`WeakValueDictionary` classes supplied by the :mod:`weakref` module are +an alternative, using weak references to construct mappings that don't keep +objects alive solely because they appear in the mapping objects. If, for +example, an image object is a value in a :class:`WeakValueDictionary`, then when +the last remaining references to that image object are the weak references held +by weak mappings, garbage collection can reclaim the object, and its +corresponding entries in weak mappings are simply deleted. :class:`WeakKeyDictionary` and :class:`WeakValueDictionary` use weak references in their implementation, setting up callback functions on the weak references |