Changing base class of a big hierarchy

[John J. Lee]

I'm trying to change a base class of a big class hierarchy.  The
hierarchy in question is 4DOM (from PyXML).  4DOM has an FtNode class
that defines __getattr__ and __setattr__ that I need to override.

Lots of classes derive from FtNode, often through further base
classes, eg.

HTMLDirectoryElement --> HTMLElement --> Element --> FtNode

There are many leaf classes like HTMLDirectoryElement.  The problem
is, I need to get new classes identical to the leaf classes, but
deriving from BrowserFtNode:

class BrowserFtNode(FtNode):
    def __init__(self, *args, **kwargs):
        ...
    def __getattr__(self, name):
        ...
    def __setattr__(self, name, value):
        ...


Obviously, I don't want to manually derive from every damned leaf
class.  I want to say "give me a new class hierarchy just like this
one, but derived from BrowserFtNode instead of FtNode".  I also don't
want to actually mutate the xml.dom module, of course because other
code may be using it.

What's the easiest way to do that?

Maybe deep-copying the module or something, then fiddling with
__bases__??  Or a metaclass?

While I'm on the subject, does anybody have code to get a list of all
classes in a package that derive from a particular class?  Or
something I could use to do that easily?


John