Does Python really follow its philosophy of "Readability counts"?

Terry Reedy tjreedy at
Fri Jan 16 11:24:15 CET 2009

Paul Rubin wrote:
> Terry Reedy <tjreedy at> writes:
>>>> Have you looked at Tim Sweeney's talk that I mentioned in another post?
>> I did.  He gives a really nice use case for Python's ability to
>> dynamically modify classes imported from a library.  (Were not you
>> arguing against that?  Or was is someone else?)
> He is talking about extending classes by something like inheritance,
> not modifying them dynamically.  This is also in the context of an
> extremely powerful static type system with existential and dependent
> types, and totality proofs for just about everything.  That is about a
> billion light years away from anything anyone has ever proposed for
> Python.

If the library framework were written in Python, one would have a choice 
between creating a parallel class hierachy (through inheritance) that 
dupicates *every* class in the original hierachy and dynamically 
patching just those classes that need to be changed.  He only discussed 
the former option because that was the only one available.  If, for 
instance, one only needed to change the base class, patching just that 
would be much easier.  Hence my comment.


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