How best to dynamically define methods (and functions)?

[Kenneth McDonald]

I can see an obvious but hacky way to define a Python function at 
runtime. I can't see any obvious way to add a method to a class at 
runtime (though I'm sure one could do just about anything by digging 
into the metaclass stuff, which I will do if needed). But pointers to 
cleaner or easier existing ways to do this would be most appreciated.

In case it's of interest in the context of the question, I need to 
define a largish set of functions (and similar methods) that define a 
XML-type markup language. Most of these functions will just be of the form

def fun(...):
    return Node('fun', ...)

so it'd definitely be nice to just create most of them automatically, 
and only do the special cases by hand.


Many thanks,
Ken