Source Code for Module advene.util.reftools

 1  """I provide utility functions and class related to weak references. 
 2  """ 
 3   
 4  from weakref import WeakValueDictionary 
 5   
 6 -class WeakValueDictWithCallback(WeakValueDictionary): 
 7      """I extend WeakValueDictionary with a configurable callback function. 
 8   
 9      The callback function must be given *before* any value is assigned, 
10      so WeakValueDictWithCallback does not accept a dict nor keyword arguments 
11      as __init__ parameters. 
12      The callback function will be invoked after a key is removed, with that key 
13      as its only argument. 
14      """ 
15 -    def __init__(self, callback): 
16          WeakValueDictionary.__init__ (self) 
17          # The superclass WeakValueDictionary assigns self._remove as a 
18          # callback to all the KeyedRef it creates. So we have to override 
19          # self._remove. 
20          # Note however that self._remobe is *not* a method because, as a 
21          # callback, it can be invoked after the dictionary is collected. 
22          # So it is a plain function, stored as an *instance* attribute. 
23          def remove(wr, _callback=callback, _original=self._remove): 
24              _original(wr) 
25              _callback(wr.key) 
26          self._remove = remove 
27