Any way of adding methods/accessors to built-in classes?

[Kenneth McDonald]

This is possible with pure Python classes. Just add the method as new 
attribute of the class. However, that won't work for the builtins.

I know that this is somewhat dangerous, and also that I could subclass 
the builtins, but not being able to do things like '[1,2,3]'.length 
drives me a little nuts. Python is about the only computer language I 
use, and I think it's certainly the best of the scripting languages, but 
there are inconsistencies in the object model and some other things I 
wish I could fix. If could could modify the builtins this way, I'd be 
willing to take the risk.

Thanks,
Ken