[Python-3000] Need help completing ABC pep

Nick Coghlan ncoghlan at gmail.com
Sat Apr 21 11:17:15 CEST 2007

Guido van Rossum wrote:
> I do see your point though: object.__hash__ makes it possible to use
> all sorts of objects as dict keys by default, as long as they don't
> implement __eq__. But perhaps this is not such a good idea and we
> should just get rid of it and add __hash__ back to specific objects
> that are useful to use as keys? (E.g. classes but not iterators, to
> take some extreme examples.)

We've tried to do this before - the point where we got stuck was the 
fact that Jython needed a separate location to store the default hash 
method (unlike CPython, Jython's id() and object.__hash__() do different 
things), and we couldn't come up with a reasonable location for it.

I agree that moving the default method from object to Hashable doesn't 
eliminate the errors that arise from redefining __eq__ without 
redefining __hash__, but at least it restricts them to those classes 
which have Hashable somewhere in their MRO.


Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia

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