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Victor Stinner @vstinner.bsky.social · 10/10/2026

My recent work on PyBytesWriter and PyUnicodeWriter C API, bugfixes, optimizations, and documentation changes: vstinner.github.io/optimize-pyb... PyBytesWriter is now 1.28x faster than Python 3.15 and PyUnicodeWriter can avoid memory copies. Detect buffer overflow in debug mode.

Painting: Luxe, Calme et Volupté (1904), by Henri Matisse.

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Victor Stinner @vstinner.bsky.social · 05/07/2026

New long article on PEP 814: Add frozendict built-in type vstinner.github.io/pep-814-add-... Donghee Na and me wrote PEP 814 to add frozendict implemented in C. Here is the long journey of adding the type to Python 3.15: implementation, stdlib changes, optimizations, complex bugs, C API, etc.

Painting: La Danse au Moulin-Rouge - Henri de Toulouse-Lautrec (1890)

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Victor Stinner @vstinner.bsky.social · 18/06/2026

I'm writing an article series on Free Threading internals. The 3rd article vstinner.github.io/free-threadi... introduces PyMutex: one byte lock with fast, inlineable lock and unlock functions for the common uncontended case. The design is based on WebKit's WTF::Lock.

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Victor Stinner @vstinner.bsky.social · 04/06/2026

I'm writing an article serie on Free Threading internals. The second article vstinner.github.io/free-threadi... analyzes immortal objects, deferred reference count, and stack references which reduce reference count contention by optimizing Py_INCREF()/Py_DECREF().

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Victor Stinner @vstinner.bsky.social · 03/06/2026

Article serie on Free Threading internals. First article on the performance problem of tracking objects lifetime: vstinner.github.io/free-threadi... Gilectomy started with atomic operations and switched to buffered ref counting. nogil solved the perf issue using Biased Reference Counting.

Painting: The Bride by Marc Chagall (1950)

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Victor Stinner @vstinner.bsky.social · 17/10/2025

In the Python C API, I dislike APIs modifying immutable objects like _PyBytes_Resize(). I designed a new PyBytesWriter API to replace this function. As usual in Python, it took multiple iterations and one year to design the API and to reach an agreement. vstinner.github.io/pep-782-pyby...

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Victor Stinner @vstinner.bsky.social · 11/09/2025

Design an API can take time. This article describes the design of the C API to import and export Python integers. It takes place between August 2023 and December 2024. In total, the discussions got more than 448 messages! vstinner.github.io/pep-757-c-ap...

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Victor Stinner @vstinner.bsky.social · 11/03/2025

Report on my 18 commits merged into Python in February 2025: vstinner.github.io/python-commi... - Reorganize C API tests - Use PyErr_FormatUnraisable() - Reorganize includes - Remove PySequence_Fast() - Fix function signature undefined behavior - Deprecate private _PyUnicodeWriter - etc.

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Victor Stinner @vstinner.bsky.social · 01/02/2025

Snapshot of FOSDEM conferences: Rust for Linux, Ladybird web browser, Poppler PDF library, women in tech history.

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