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base repository: python/cpython
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head repository: eendebakpt/cpython
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compare: bytes-join-exact-fast
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  • 1 commit
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Commits on Oct 10, 2026

  1. Add a fast path to bytes.join() for exact bytes items 

    When all items are exact bytes objects, copy straight from the items
instead of building a Py_buffer and taking a reference for each one,
and store a one-byte separator directly.

The fast path is used when the GIL is not released during the copy:
results below the existing 1 MiB threshold in the default build, and
results of any size in the free-threaded build, where the caller holds
the critical section of the sequence.

In the general path, release exact bytes items with a plain decref:
bytes has no bf_releasebuffer, so PyBuffer_Release() does nothing more.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
    @eendebakpt @claude
    eendebakpt and claude committed Oct 10, 2026
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