Cast into custom type

Diez B. Roggisch deets at
Tue Nov 3 11:00:23 CET 2009

Henning Bredel schrieb:
> Hi,
> I created a plugin mechanism for my application orientating
> at the mechanism described by Martin Alchy in
> Now I'd like to call methods like `initialize(parent)' when
> the user chooses to use a plugin. As described in the blog
> mentioned above, I only have access to the general type called
> `PluginMount' (holding all the actual plugin instances).
> I tried to define "abstract" methods in PluginMount type 
> raising a `NotImplementedError' but it seems, there is no
> late binding (similar to Java), so the right method would be
> called. Only the message 
>   TypeError: unbound method initialize() must be called 
>   with GeoCache instance as first argument (got PluginMount 
>   instance instead)
> `GeoCache' would be the plugin type. What is strange, is the
> fact, that when asking what instances are hold by PluginMount
>    [<class 'geocacheplugin.GeoCache'>]
> is listed. So it seems, that no late binding is applied when
> calling the `initialize(self, parent)' method.
> I'm quite new using Python, so this might be a quite basic 
> question caused by some misunderstandings in general. Feel
> free to point me to appropriate site to solve my problem.

It seems that GeoCache is not a subclass of PluginMount.


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