>  I am trying to derive a new class from class Image in Image.py in
>  Fredrik Lundh's PIL (Python Imaging Library). I'm not entirely sure of
>  the reasoning behind the Image class structure, but it uses a factory
>  function in the module called new to create new instances of class
>  Image. This is, I guess, so that images can be created in different
>  ways (ie from a file with the open() factory function).

The Image class is just a wrapper for the internal ImagingCore type;
it was never really designed for general subclassing...  But as you
pointed out, the _makeself method allows you to get some control over
what all those factory methods in there really returns.

>  I guess a different way of looking at it is - Is there any way of
>  initialising the baseClass part from a derived class __init__()
>  given a already existing instance of the base class?

Maybe you could do something like:

	class XImage(Image):

	    def __init__(self, mode, size, bg = 0):

		# initialize base class part
		Image.__init__(self)

		# whatever

	    def _makeself(self, im):

		# wrap ImagingCore object in a suitable Python class

Cheers	/F

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