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Subject: Re: 'isimmutable' and 'ImmutableNester'
Date: Tue, 12 Nov 2013 10:48:50 -0500
Cc: python-list@python.org
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Xref: csiph.com comp.lang.python:59213

On Tue, Nov 12, 2013, at 4:39, Frank-Rene Sch=C3=A4fer wrote:
> > All you've done is proven that you can subvert things. By fiddling
> > with __hash__, __eq__, and so on, you can make sets and dicts behave
> > very oddly. Means nothing.
>=20
> To the contrary, it means everything about what 'isimmutable' could
> contribute: security against advert or inadvert insertion of mutable
> objects.

If an object can lie about its hashability, it can lie to your function
too... unless you don't intend to provide a way for a _genuinely_
immutable class to say so.