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gh-153234: Add NEWS entry for dict.fromkeys fast-clone optimization
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‎Misc/NEWS.d/next/Core_and_Builtins/2026-07-07-01-24-00.gh-issue-153234.xK9mPq.rst‎

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Optimize :meth:`dict.fromkeys` when the source iterable is a compact combined
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dict by cloning the underlying ``PyDictKeysObject`` in a single ``memcpy``
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and filling values in one pass, instead of calling ``insertdict()`` for every
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key. This avoids O(n) hash lookups and collision probing on the target dict.

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