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Tue Mar 23 19:04:37 CET 2010 · https://mail.python.org/pipermail/python-dev/2010-March/098762.html

On Tue, Mar 23, 2010 at 5:48 PM, Adam Olsen <rhamph at gmail.com> wrote:
> a = Decimal('nan')
> a != a
>
> They don't follow the behaviour required for being hashable.

What's this required behaviour?  The only rule I'm aware of is that if
a == b then hash(a) == hash(b).  That's not violated here.

Note that containment tests check identity before equality, so there's
no problem with putting (float) nans in sets or dicts:

>>> x = float('nan')
>>> s = {x}
>>> x in s
True

Mark

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[Python-Dev] Mixing float and Decimal -- thread reboot