Class WeakValueDictWithCallback

source code

      UserDict.UserDict --+    
                          |    
weakref.WeakValueDictionary --+
                              |
                             WeakValueDictWithCallback

I extend WeakValueDictionary with a configurable callback function.

The callback function must be given *before* any value is assigned, so WeakValueDictWithCallback does not accept a dict nor keyword arguments as __init__ parameters. The callback function will be invoked after a key is removed, with that key as its only argument.