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bpo-43475: Add what's new entry for NaN hash changes (GH-26725)

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Mark Dickinson 2021-06-15 19:48:35 +01:00 committed by GitHub
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@ -836,6 +836,13 @@ Other Language Changes
effectless under ``from __future__ import annotations``.
(Contributed by Batuhan Taskaya in :issue:`42725`.)
* Hashes of NaN values of both :class:`float` type and
:class:`decimal.Decimal` type now depend on object identity. Formerly, they
always hashed to ``0`` even though NaN values are not equal to one another.
This caused potentially quadratic runtime behavior due to excessive hash
collisions when creating dictionaries and sets containing multiple NaNs.
(Contributed by Raymond Hettinger in :issue:`43475`.)
New Modules
===========