Imposing metaclass on library

[Lulu of the Lotus-Eaters]

|Lulu of the Lotus-Eaters <mertz at gnosis.cx> wrote:
|> Here is the situation:  I have a library of classes, and I do not want
|> to modify the library.  But I would like to cause all -descendents- of
|> library classes to be created with a custom metaclass (within my
|> application that uses the library).

mis6 at pitt.edu (Michele Simionato) wrote previously:
|I wrote the attached program before reading your posting. Maybe a modification
|of that can help you. Warning: it is highly untested !!

I think this variant on Michele's suggestion is a bit more general.  I
need to play with it a bit more to make sure it entirely does what I
want, but it looks mostly OK:

    """Import a module using a custom metaclass for class creation

    As a byproduct, classic classic are converted to new style classes
    """
    import inspect

    class import_with_metaclass(object):
        "This is a class factory, not a metaclass"
        def __init__(cls, module, metaclass):
            class Meta(object): __metaclass__ = metaclass
            mod = __import__(module)
            for key, val in mod.__dict__.items():
                if inspect.isclass(val):
                    setattr(cls, key, type(key, (val, Meta),{}))

    #e.g.: random = import_with_metaclass('random', MetaTrace)

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