Sourced from pyo3's releases.

PyO3 0.26.0

This version solidifies support for Python 3.14 and free-threaded Python 3.14t. A number of PyO3 APIs have been renamed to reflect the fact the GIL is no longer a universal feature of all Python implementations. For example:

• Python::with_gil is now known as Python::attach
• Python::allow_threads is now known as Python::detach
• pyo3::prepare_freethreaded_python is now known as Python::initialize()

The minimum supported Rust version has been increased to Rust 1.74.

An optional dependency on the bytes crate has been added to allow support for converting bytes::Bytes to / from Python.

The PyObject type alias for Py<PyAny> has also been deprecated; the Py and Bound smart pointers have been the primary interface for all Python-facing types since PyO3 0.21 and the PyObject type alias had been a frequent source of confusion.

There are also many other incremental improvements, bug fixes and smaller features.

Please consult the migration guide for help upgrading.

Thank you to everyone who contributed code, documentation, design ideas, bug reports, and feedback. The following contributors' commits are included in this release:

@​ahlinc @​alex @​anilbey @​bschoenmaeckers @​Cheukting @​codeguru42 @​davidhewitt @​decathorpe @​dependabot[bot] @​drewkett @​FlickerSoul @​Icxolu @​jder @​jessekrubin @​jjmarchewitz @​kemingy @​msimacek @​musicinmybrain @​ngoldbaum @​Nnamdi-sys @​nucccc @​olp-cs @​robsdedude @​rrricharrrd @​sxlijin @​timfel @​tonybaloney @​Tpt @​wxianxin @​xushiyan @​yogevm15

... (truncated)

Sourced from pyo3's changelog.

[0.26.0] - 2025-08-29

Packaging

• Bump hashbrown dependency to 0.15. #5152
• Update MSRV to 1.74. #5171
• Set the same maximum supported version for alternative interpreters as for CPython. #5192
• Add optional bytes dependency to add conversions for bytes::Bytes. #5252
• Publish new crate pyo3-introspection to pair with the experimental-inspect feature. #5300
• The PYO3_BUILD_EXTENSION_MODULE now causes the same effect as the extension-module feature. Eventually we expect maturin and setuptools-rust to set this environment variable automatically. Users with their own build systems will need to do the same. #5343

Added

• Add #[pyo3(warn(message = "...", category = ...))] attribute for automatic warnings generation for #[pyfunction] and #[pymethods]. #4364
• Add PyMutex, available on Python 3.13 and newer. #4523
• Add FFI definition PyMutex_IsLocked, available on Python 3.14 and newer. #4523
• Add PyString::from_encoded_object. #5017
• experimental-inspect: add basic input type annotations. #5089
• Add FFI function definitions for PyFrameObject from CPython 3.13. #5154
• experimental-inspect: tag modules created using #[pymodule] or #[pymodule_init] functions as incomplete. #5207
• experimental-inspect: add basic return type support. #5208
• Add PyCode::compile and PyCodeMethods::run to create and execute code objects. #5217
• Add PyOnceLock type for thread-safe single-initialization. #5223
• Add PyClassGuard(Mut) pyclass holders. In the future they will replace PyRef(Mut). #5233
• experimental-inspect: allow annotations in #[pyo3(signature)] signature attribute. #5241
• Implement MutexExt for parking_lot's/lock_api ReentrantMutex. #5258
• experimental-inspect: support class associated constants. #5272
• Add Bound::cast family of functions superseding the PyAnyMethods::downcast family. #5289
• Add FFI definitions Py_Version and Py_IsFinalizing. #5317
• experimental-inspect: add output type annotation for #[pyclass]. #5320
• experimental-inspect: support #[pyclass(eq, eq_int, ord, hash, str)]. #5338
• experimental-inspect: add basic support for #[derive(FromPyObject)] (no struct fields support yet). #5339
• Add Python::try_attach. #5342

Changed

• Use Py_TPFLAGS_DISALLOW_INSTANTIATION instead of a __new__ which always fails for a #[pyclass] without a #[new] on Python 3.10 and up. #4568
• PyModule::from_code now defaults file_name to <string> if empty. #4777
• Deprecate PyString::from_object in favour of PyString::from_encoded_object. #5017
• When building with abi3 for a Python version newer than pyo3 supports, automatically fall back to an abi3 build for the latest supported version. #5144
• Change is_instance_of trait bound from PyTypeInfo to PyTypeCheck. #5146
• Many PyO3 proc macros now report multiple errors instead of only the first one. #5159
• Change MutexExt return type to be an associated type. #5201
• Use PyCallArgs for Py::call and friends so they're equivalent to their Bound counterpart. #5206
• Rename Python::with_gil to Python::attach. #5209
• Rename Python::allow_threads to Python::detach #5221
• Deprecate GILOnceCell type in favour of PyOnceLock. #5223
• Rename pyo3::prepare_freethreaded_python to Python::initialize. #5247
• Convert PyMemoryError into/from io::ErrorKind::OutOfMemory. #5256
• Deprecate GILProtected. #5285

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• 4502c2e ci: fix release job token permissions (#5374)
• a43cf79 release: 0.26.0 (#5367)
• f4d533f Clarity and grammar fixes in free-threading guide (#5369)
• ed030a7 fixes #5202 -- treat the PYO3_BUILD_EXTENSION_MODULE env var the same as te...
• 1775baf Use links to latest CPython stable release in docs (#5366)
• acaa2be Update free-threading docs for 0.26 (#5355)
• 9cc0bb6 fix "no constructor defined" messages on PyPy (#5329)
• 9aa53f4 Generate introspection for #[pyclass(eq, eq_int, ord, hash, str)] (#5338)
• a0c7d2c fixup Py::cast_bound (#5361)
• 50b0193 fix warning leaking out of test in test_methods (#5362)
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