Starting with version 1.8.0, pybind11 releases use a semantic versioning policy.

Changes will be added here periodically from the “Suggested changelog entry” block in pull request descriptions.


Changes will be summarized here periodically.

Version 2.12.0 (March 27, 2025)#

New Features:

  • pybind11 now supports compiling for NumPy 2. Most code shouldn’t change (see v2.12 for details). However, if you experience issues you can define PYBIND11_NUMPY_1_ONLY to disable the new support for now, but this will be removed in the future. #5050

  • pybind11/gil_safe_call_once.h was added (it needs to be included explicitly). The primary use case is GIL-safe initialization of C++ static variables. #4877

  • Support move-only iterators in py::make_iterator, py::make_key_iterator, py::make_value_iterator. #4834

  • Two simple py::set_error() functions were added and the documentation was updated accordingly. In particular, py::exception<>::operator() was deprecated (use one of the new functions instead). The documentation for py::exception<> was further updated to not suggest code that may result in undefined behavior. #4772

Bug fixes:

  • Removes potential for Undefined Behavior during process teardown. #4897

  • Improve compatibility with the nvcc compiler (especially CUDA 12.1/12.2). #4893

  • pybind11/numpy.h now imports NumPy’s multiarray and _internal submodules with paths depending on the installed version of NumPy (for compatibility with NumPy 2). #4857

  • Builtins collections names in docstrings are now consistently rendered in lowercase (list, set, dict, tuple), in accordance with PEP 585. #4833

  • Added py::typing::Iterator<T>, py::typing::Iterable<T>. #4832

  • Render py::function as Callable in docstring. #4829

  • Also bump PYBIND11_INTERNALS_VERSION for MSVC, which unlocks two new features without creating additional incompatibilities. #4819

  • Guard against crashes/corruptions caused by modules built with different MSVC versions. #4779

  • A long-standing bug in the handling of Python multiple inheritance was fixed. See PR #4762 for the rather complex details. #4762

  • Fix bind_map with using declarations. #4952

  • Qualify py::detail::concat usage to avoid ADL selecting one from somewhere else, such as modernjson’s concat. #4955

  • Use new PyCode API on Python 3.12+. #4916

  • Minor cleanup from warnings reported by Clazy. #4988

  • Remove typing and duplicate class_ for KeysView/ValuesView/ItemsView. #4985

  • Use PyObject_VisitManagedDict() and PyObject_ClearManagedDict() on Python 3.13 and newer. #4973

  • Update make_static_property_type() to make it compatible with Python 3.13. #4971

  • Render typed iterators for make_iterator, make_key_iterator, make_value_iterator. #4876

  • Add several missing type name specializations. #5073

  • Change docstring render for py::buffer, py::sequence and py::handle (to Buffer, Sequence, Any). #4831

  • Fixed base_enum.__str__ docstring. #4827

  • Enforce single line docstring signatures. #4735

  • Special ‘typed’ wrappers now available in typing.h to annotate tuple, dict, list, set, and function. #4259

  • Create handle_type_name specialization to type-hint variable length tuples. #5051

  • Setting PYBIND11_FINDPYTHON to OFF will force the old FindPythonLibs mechanism to be used. #5042

  • Skip empty PYBIND11_PYTHON_EXECUTABLE_LAST for the first cmake run. #4856

  • Fix FindPython mode exports & avoid pkg_resources if importlib.metadata available. #4941

  • Python_ADDITIONAL_VERSIONS (classic search) now includes 3.12.

  • pybind11.pc is now relocatable by default as long as install destinations are not absolute paths. #4830

  • Correctly detect CMake FindPython removal when used as a subdirectory. #4806

  • Don’t require the libs component on CMake 3.18+ when using PYBIND11_FINDPYTHON (fixes manylinux builds). #4805

  • pybind11_strip is no longer automatically applied when CMAKE_BUILD_TYPE is unset. #4780

  • Support DEBUG_POSFIX correctly for debug builds. #4761

  • Hardcode lto/thin lto for Emscripten cross-compiles. #4642

  • Upgrade maximum supported CMake version to 3.27 to fix CMP0148 warnings. #4786


  • Small fix to grammar in functions.rst. #4791

  • Remove upper bound in example pyproject.toml for setuptools. #4774


  • CI: Update NVHPC to 23.5 and Ubuntu 20.04. #4764

  • Test on PyPy 3.10. #4714


  • Use Ruff formatter instead of Black. #4912

  • An assert() was added to help Coverty avoid generating a false positive. #4817

Version 2.11.1 (July 17, 2023)#


  • PYBIND11_NO_ASSERT_GIL_HELD_INCREF_DECREF is now provided as an option for disabling the default-on PyGILState_Check()’s in pybind11::handle’s inc_ref() & dec_ref(). #4753

  • PYBIND11_ASSERT_GIL_HELD_INCREF_DECREF was disabled for PyPy in general (not just PyPy Windows). #4751

Version 2.11.0 (July 14, 2023)#

New features:

  • The newly added pybind11::detail::is_move_constructible trait can be specialized for cases in which std::is_move_constructible does not work as needed. This is very similar to the long-established pybind11::detail::is_copy_constructible. #4631

  • Introduce recursive_container_traits. #4623

  • pybind11/type_caster_pyobject_ptr.h was added to support automatic wrapping of APIs that make use of PyObject *. This header needs to included explicitly (i.e. it is not included implicitly with pybind/pybind11.h). #4601

  • format_descriptor<> & npy_format_descriptor<> PyObject * specializations were added. The latter enables py::array_t<PyObject *> to/from-python conversions. #4674

  • buffer_info gained an item_type_is_equivalent_to<T>() member function. #4674

  • The capsule API gained a user-friendly constructor (py::capsule(ptr, "name", dtor)). #4720


  • PyGILState_Check()’s in pybind11::handle’s inc_ref() & dec_ref() are now enabled by default again. #4246

  • py::initialize_interpreter() using PyConfig_InitPythonConfig() instead of PyConfig_InitIsolatedConfig(), to obtain complete sys.path. #4473

  • Cast errors now always include Python type information, even if PYBIND11_DETAILED_ERROR_MESSAGES is not defined. This increases binary sizes slightly (~1.5%) but the error messages are much more informative. #4463

  • The docstring generation for the std::array-list caster was fixed. Previously, signatures included the size of the list in a non-standard, non-spec compliant way. The new format conforms to PEP 593. Tooling for processing the docstrings may need to be updated accordingly. #4679

  • Setter return values (which are inaccessible for all practical purposes) are no longer converted to Python (only to be discarded). #4621

  • Allow lambda specified to function definition to be noexcept(true) in C++17. #4593

  • Get rid of recursive template instantiations for concatenating type signatures on C++17 and higher. #4587

  • Compatibility with Python 3.12 (beta). Note that the minimum pybind11 ABI version for Python 3.12 is version 5. (The default ABI version for Python versions up to and including 3.11 is still version 4.). #4570

  • With PYBIND11_INTERNALS_VERSION 5 (default for Python 3.12+), MSVC builds use std::hash<std::type_index> and std::equal_to<std::type_index> instead of string-based type comparisons. This resolves issues when binding types defined in the unnamed namespace. #4319

  • Python exception __notes__ (introduced with Python 3.11) are now added to the error_already_set::what() output. #4678

Build system improvements:

  • CMake 3.27 support was added, CMake 3.4 support was dropped. FindPython will be used if FindPythonInterp is not present. #4719

  • Update clang-tidy to 15 in CI. #4387

  • Moved the linting framework over to Ruff. #4483

  • Skip lto checks and target generation when CMAKE_INTERPROCEDURAL_OPTIMIZATION is defined. #4643

  • No longer inject -stdlib=libc++, not needed for modern Pythons (macOS 10.9+). #4639

  • PyPy 3.10 support was added, PyPy 3.7 support was dropped. #4728

  • Testing with Python 3.12 beta releases was added. #4713

Version 2.10.4 (Mar 16, 2023)#


  • python3 -m pybind11 gained a --version option (prints the version and exits). #4526

Bug Fixes:

  • Fix a warning when pydebug is enabled on Python 3.11. #4461

  • Ensure gil_scoped_release RAII is non-copyable. #4490

  • Ensure the tests dir does not show up with new versions of setuptools. #4510

  • Better stacklevel for a warning in setuptools helpers. #4516

Version 2.10.3 (Jan 3, 2023)#


  • Temporarily made our GIL status assertions (added in 2.10.2) disabled by default (re-enable manually by defining PYBIND11_ASSERT_GIL_HELD_INCREF_DECREF, will be enabled in 2.11). #4432

  • Improved error messages when inc_ref/dec_ref are called with an invalid GIL state. #4427 #4436

Bug Fixes:

  • Some minor touchups found by static analyzers. #4440

Version 2.10.2 (Dec 20, 2022)#


  • scoped_interpreter constructor taking PyConfig. #4330

  • pybind11/eigen/tensor.h adds converters to and from Eigen::Tensor and Eigen::TensorMap. #4201

  • PyGILState_Check()’s were integrated to pybind11::handle inc_ref() & dec_ref(). The added GIL checks are guarded by PYBIND11_ASSERT_GIL_HELD_INCREF_DECREF, which is the default only if NDEBUG is not defined. (Made non-default in 2.10.3, will be active in 2.11) #4246

  • Add option for enable/disable enum members in docstring. #2768

  • Fixed typing of KeysView, ValuesView and ItemsView in bind_map. #4353

Bug fixes:

  • Bug fix affecting only Python 3.6 under very specific, uncommon conditions: move PyEval_InitThreads() call to the correct location. #4350

  • Fix segfault bug when passing foreign native functions to functional.h. #4254

Build system improvements:

  • Support setting PYTHON_LIBRARIES manually for Windows ARM cross-compilation (classic mode). #4406

  • Extend IPO/LTO detection for ICX (a.k.a IntelLLVM) compiler. #4402

  • Allow calling find_package(pybind11 CONFIG) multiple times from separate directories in the same CMake project and properly link Python (new mode). #4401

  • multiprocessing_set_spawn in pytest fixture for added safety. #4377

  • Fixed a bug in two pybind11/tools cmake scripts causing “Unknown arguments specified” errors. #4327

Version 2.10.1 (Oct 31, 2022)#

This is the first version to fully support embedding the newly released Python 3.11.


  • Allow pybind11::capsule constructor to take null destructor pointers. #4221

  • embed.h was changed so that PYTHONPATH is used also with Python 3.11 (established behavior). #4119

  • A PYBIND11_SIMPLE_GIL_MANAGEMENT option was added (cmake, C++ define), along with many additional tests in The option may be useful to try when debugging GIL-related issues, to determine if the more complex default implementation is or is not to blame. See #4216 for background. WARNING: Please be careful to not create ODR violations when using the option: everything that is linked together with mutual symbol visibility needs to be rebuilt. #4216

  • PYBIND11_EXPORT_EXCEPTION was made non-empty only under macOS. This makes Linux builds safer, and enables the removal of warning suppression pragmas for Windows. #4298

Bug fixes:

  • Fixed a bug where UnicodeDecodeError was not propagated from various py::str ctors when decoding surrogate utf characters. #4294

  • Revert perfect forwarding for make_iterator. This broke at least one valid use case. May revisit later. #4234

  • Fix support for safe casts to void* (regression in 2.10.0). #4275

  • Fix char8_t support (regression in 2.9). #4278

  • Unicode surrogate character in Python exception message leads to process termination in error_already_set::what(). #4297

  • Fix MSVC 2019 v.1924 & C++14 mode error for overload_cast. #4188

  • Make augmented assignment operators non-const for the object-api. Behavior was previously broken for augmented assignment operators. #4065

  • Add proper error checking to C++ bindings for Python list append and insert. #4208

  • Work-around for Nvidia’s CUDA nvcc compiler in versions 11.4.0 - 11.8.0. #4220

  • A workaround for PyPy was added in the py::error_already_set implementation, related to PR #1895 released with v2.10.0. #4079

  • Fixed compiler errors when C++23 std::forward_like is available. #4136

  • Properly raise exceptions in contains methods (like when an object in unhashable). #4209

  • Further improve another error in exception handling. #4232

  • get_local_internals() was made compatible with finalize_interpreter(), fixing potential freezes during interpreter finalization. #4192

Performance and style:

  • Reserve space in set and STL map casters if possible. This will prevent unnecessary rehashing / resizing by knowing the number of keys ahead of time for Python to C++ casting. This improvement will greatly speed up the casting of large unordered maps and sets. #4194

  • GIL RAII scopes are non-copyable to avoid potential bugs. #4183

  • Explicitly default all relevant ctors for pytypes in the PYBIND11_OBJECT macros and enforce the clang-tidy checks modernize-use-equals-default in macros as well. #4017

  • Optimize iterator advancement in C++ bindings. #4237

  • Use the modern PyObject_GenericGetDict and PyObject_GenericSetDict for handling dynamic attribute dictionaries. #4106

  • Document that users should use PYBIND11_NAMESPACE instead of using pybind11 when opening namespaces. Using namespace declarations and namespace qualification remain the same as pybind11. This is done to ensure consistent symbol visibility. #4098

  • Mark detail::forward_like as constexpr. #4147

  • Optimize unpacking_collector when processing arg_v arguments. #4219

  • Optimize casting C++ object to None. #4269

Build system improvements:

  • CMake: revert overwrite behavior, now opt-in with PYBIND11_PYTHONLIBS_OVERRWRITE OFF. #4195

  • Include a pkg-config file when installing pybind11, such as in the Python package. #4077

  • Avoid stripping debug symbols when CMAKE_BUILD_TYPE is set to DEBUG instead of Debug. #4078

  • Followup to #3948, fixing vcpkg again. #4123

Version 2.10.0 (Jul 15, 2022)#

Removed support for Python 2.7, Python 3.5, and MSVC 2015. Support for MSVC 2017 is limited due to availability of CI runners; we highly recommend MSVC 2019 or 2022 be used. Initial support added for Python 3.11.

New features:

  • py::anyset & py::frozenset were added, with copying (cast) to std::set (similar to set). #3901

  • Support bytearray casting to string. #3707

  • type_caster<std::monostate> was added. std::monostate is a tag type that allows std::variant to act as an optional, or allows default construction of a std::variant holding a non-default constructible type. #3818

  • pybind11::capsule::set_name added to mutate the name of the capsule instance. #3866

  • NumPy: dtype constructor from type number added, accessors corresponding to Python API dtype.num, dtype.byteorder, dtype.flags and dtype.alignment added. #3868


  • Python 3.6 is now the minimum supported version. #3688 #3719

  • The minimum version for MSVC is now 2017. #3722

  • Fix issues with CPython 3.11 betas and add to supported test matrix. #3923

  • error_already_set is now safer and more performant, especially for exceptions with long tracebacks, by delaying computation. #1895

  • Improve exception handling in python str bindings. #3826

  • The bindings for capsules now have more consistent exception handling. #3825

  • PYBIND11_OBJECT_CVT and PYBIND11_OBJECT_CVT_DEFAULT macro can now be used to define classes in namespaces other than pybind11. #3797

  • Error printing code now uses PYBIND11_DETAILED_ERROR_MESSAGES instead of requiring NDEBUG, allowing use with release builds if desired. #3913

  • Implicit conversion of the literal 0 to pybind11::handle is now disabled. #4008

Bug fixes:

  • Fix exception handling when pybind11::weakref() fails. #3739

  • module_::def_submodule was missing proper error handling. This is fixed now. #3973

  • The behavior or error_already_set was made safer and the highly opaque “Unknown internal error occurred” message was replaced with a more helpful message. #3982

  • error_already_set::what() now handles non-normalized exceptions correctly. #3971

  • Support older C++ compilers where filesystem is not yet part of the standard library and is instead included in std::experimental::filesystem. #3840

  • Fix -Wfree-nonheap-object warnings produced by GCC by avoiding returning pointers to static objects with return_value_policy::take_ownership. #3946

  • Fix cast from pytype rvalue to another pytype. #3949

  • Ensure proper behavior when garbage collecting classes with dynamic attributes in Python >=3.9. #4051

  • A couple long-standing PYBIND11_NAMESPACE __attribute__((visibility("hidden"))) inconsistencies are now fixed (affects only unusual environments). #4043

  • pybind11::detail::get_internals() is now resilient to in-flight Python exceptions. #3981

  • Arrays with a dimension of size 0 are now properly converted to dynamic Eigen matrices (more common in NumPy 1.23). #4038

  • Avoid catching unrelated errors when importing NumPy. #3974

Performance and style:

  • Added an accessor overload of (object &&key) to reference steal the object when using python types as keys. This prevents unnecessary reference count overhead for attr, dictionary, tuple, and sequence look ups. Added additional regression tests. Fixed a performance bug the caused accessor assignments to potentially perform unnecessary copies. #3970

  • Perfect forward all args of make_iterator. #3980

  • Avoid potential bug in pycapsule destructor by adding an error_guard to one of the dtors. #3958

  • Optimize dictionary access in strip_padding for numpy. #3994

  • stl_bind.h bindings now take slice args as a const-ref. #3852

  • Made slice constructor more consistent, and improve performance of some casters by allowing reference stealing. #3845

  • Change numpy dtype from_args method to use const ref. #3878

  • Follow rule of three to ensure PyErr_Restore is called only once. #3872

  • Added missing perfect forwarding for make_iterator functions. #3860

  • Optimize c++ to python function casting by using the rvalue caster. #3966

  • Optimize Eigen sparse matrix casting by removing unnecessary temporary. #4064

  • Avoid potential implicit copy/assignment constructors causing double free in strdup_gaurd. #3905

  • Enable clang-tidy checks misc-definitions-in-headers, modernize-loop-convert, and modernize-use-nullptr. #3881 #3988

Build system improvements:

  • CMake: Fix file extension on Windows with cp36 and cp37 using FindPython. #3919

  • CMake: Support multiple Python targets (such as on vcpkg). #3948

  • CMake: Fix issue with NVCC on Windows. #3947

  • CMake: Drop the bitness check on cross compiles (like targeting WebAssembly via Emscripten). #3959

  • Add MSVC builds in debug mode to CI. #3784

  • MSVC 2022 C++20 coverage was added to GitHub Actions, including Eigen. #3732, #3741

Backend and tidying up:

  • New theme for the documentation. #3109

  • Remove idioms in code comments. Use more inclusive language. #3809

  • #include <iostream> was removed from the pybind11/stl.h header. Your project may break if it has a transitive dependency on this include. The fix is to “Include What You Use”. #3928

  • Avoid <command> usage in internal tests. #3734

Version 2.9.2 (Mar 29, 2022)#


  • Enum now has an __index__ method on Python <3.8 too. #3700

  • Local internals are now cleared after finalizing the interpreter. #3744

Bug fixes:

  • Better support for Python 3.11 alphas. #3694

  • PYBIND11_TYPE_CASTER now uses fully qualified symbols, so it can be used outside of pybind11::detail. #3758

  • Some fixes for PyPy 3.9. #3768

  • Fixed a potential memleak in PyPy in get_type_override. #3774

  • Fix usage of VISIBILITY_INLINES_HIDDEN. #3721

Build system improvements:

  • Uses sysconfig module to determine installation locations on Python >= 3.10, instead of distutils which has been deprecated. #3764

  • Support Catch 2.13.5+ (supporting GLIBC 2.34+). #3679

  • Fix test failures with numpy 1.22 by ignoring whitespace when comparing str() of dtypes. #3682

Backend and tidying up:

  • clang-tidy: added readability-qualified-auto, readability-braces-around-statements, cppcoreguidelines-prefer-member-initializer, clang-analyzer-optin.performance.Padding, cppcoreguidelines-pro-type-static-cast-downcast, and readability-inconsistent-declaration-parameter-name. #3702, #3699, #3716, #3709

  • clang-format was added to the pre-commit actions, and the entire code base automatically reformatted (after several iterations preparing for this leap). #3713

Version 2.9.1 (Feb 2, 2022)#


  • If possible, attach Python exception with py::raise_from to TypeError when casting from C++ to Python. This will give additional info if Python exceptions occur in the caster. Adds a test case of trying to convert a set from C++ to Python when the hash function is not defined in Python. #3605

  • Add a mapping of C++11 nested exceptions to their Python exception equivalent using py::raise_from. This attaches the nested exceptions in Python using the __cause__ field. #3608

  • Propagate Python exception traceback using raise_from if a pybind11 function runs out of overloads. #3671

  • py::multiple_inheritance is now only needed when C++ bases are hidden from pybind11. #3650 and #3659

Bug fixes:

  • Remove a boolean cast in numpy.h that causes MSVC C4800 warnings when compiling against Python 3.10 or newer. #3669

  • Render py::bool_ and py::float_ as bool and float respectively. #3622

Build system improvements:

  • Fix CMake extension suffix computation on Python 3.10+. #3663

  • Allow CMAKE_ARGS to override CMake args in pybind11’s own #3577

  • Remove a few deprecated c-headers. #3610

  • More uniform handling of test targets. #3590

  • Add clang-tidy readability check to catch potentially swapped function args. #3611

Version 2.9.0 (Dec 28, 2021)#

This is the last version to support Python 2.7 and 3.5.

New Features:

  • Allow py::args to be followed by other arguments; the remaining arguments are implicitly keyword-only, as if a py::kw_only{} annotation had been used. #3402


  • Make str/bytes/memoryview more interoperable with std::string_view. #3521

  • Replace _ with const_name in internals, avoid defining pybind::_ if _ defined as macro (common gettext usage) #3423

Bug fixes:

  • Fix a rare warning about extra copy in an Eigen constructor. #3486

  • Fix caching of the C++ overrides. #3465

  • Add missing std::forward calls to some cpp_function overloads. #3443

  • Support PyPy 7.3.7 and the PyPy3.8 beta. Test python-3.11 on PRs with the python dev label. #3419

  • Replace usage of deprecated Eigen::MappedSparseMatrix with Eigen::Map<Eigen::SparseMatrix<...>> for Eigen 3.3+. #3499

  • Tweaks to support Microsoft Visual Studio 2022. #3497

Build system improvements:

  • Nicer CMake printout and IDE organisation for pybind11’s own tests. #3479

  • CMake: report version type as part of the version string to avoid a spurious space in the package status message. #3472

  • Flags starting with -g in $CFLAGS and $CPPFLAGS are no longer overridden by .Pybind11Extension. #3436

  • Ensure ThreadPool is closed in setup_helpers. #3548

  • Avoid LTS on mips64 and ppc64le (reported broken). #3557

v2.8.1 (Oct 27, 2021)#

Changes and additions:

  • The simple namespace creation shortcut added in 2.8.0 was deprecated due to usage of CPython internal API, and will be removed soon. Use py::module_::import("types").attr("SimpleNamespace"). #3374

  • Add C++ Exception type to throw and catch AttributeError. Useful for defining custom __setattr__ and __getattr__ methods. #3387


  • Fixed the potential for dangling references when using properties with std::optional types. #3376

  • Modernize usage of PyCodeObject on Python 3.9+ (moving toward support for Python 3.11a1) #3368

  • A long-standing bug in eigen.h was fixed (originally PR #3343). The bug was unmasked by newly added static_assert’s in the Eigen 3.4.0 release. #3352

  • Support multiple raw inclusion of CMake helper files ( does this for multi-config generators). #3420

  • Fix harmless warning on upcoming CMake 3.22. #3368

  • Fix 2.8.0 regression with MSVC 2017 + C++17 mode + Python 3. #3407

  • Fix 2.8.0 regression that caused undefined behavior (typically segfaults) in make_key_iterator/make_value_iterator if dereferencing the iterator returned a temporary value instead of a reference. #3348

v2.8.0 (Oct 4, 2021)#

New features:

  • Added py::raise_from to enable chaining exceptions. #3215

  • Allow exception translators to be optionally registered local to a module instead of applying globally across all pybind11 modules. Use register_local_exception_translator(ExceptionTranslator&& translator) instead of register_exception_translator(ExceptionTranslator&& translator) to keep your exception remapping code local to the module. #2650

  • Add make_simple_namespace function for instantiating Python SimpleNamespace objects. Deprecated in 2.8.1. #2840

  • pybind11::scoped_interpreter and initialize_interpreter have new arguments to allow sys.argv initialization. #2341

  • Allow Python builtins to be used as callbacks in CPython. #1413

  • Added view to view arrays with a different datatype. #987

  • Implemented reshape on arrays. #984

  • Enable defining custom __new__ methods on classes by fixing bug preventing overriding methods if they have non-pybind11 siblings. #3265

  • Add make_value_iterator(), and fix make_key_iterator() to return references instead of copies. #3293

  • Improve the classes generated by bind_map: #3310

    • Change .items from an iterator to a dictionary view.

    • Add .keys and .values (both dictionary views).

    • Allow __contains__ to take any object.

  • pybind11::custom_type_setup was added, for customizing the PyHeapTypeObject corresponding to a class, which may be useful for enabling garbage collection support, among other things. #3287


  • Set __file__ constant when running eval_file in an embedded interpreter. #3233

  • Python objects and (C++17) std::optional now accepted in py::slice constructor. #1101

  • The pybind11 proxy types str, bytes, bytearray, tuple, list now consistently support passing ssize_t values for sizes and indexes. Previously, only size_t was accepted in several interfaces. #3219

  • Avoid evaluating PYBIND11_TLS_REPLACE_VALUE arguments more than once. #3290


  • Bug fix: enum value’s __int__ returning non-int when underlying type is bool or of char type. #1334

  • Fixes bug in setting error state in Capsule’s pointer methods. #3261

  • A long-standing memory leak in py::cpp_function::initialize was fixed. #3229

  • Fixes thread safety for some pybind11::type_caster which require lifetime extension, such as for std::string_view. #3237

  • Restore compatibility with gcc 4.8.4 as distributed by ubuntu-trusty, linuxmint-17. #3270

Build system improvements:

  • Fix regression in CMake Python package config: improper use of absolute path. #3144

  • Cached Python version information could become stale when CMake was re-run with a different Python version. The build system now detects this and updates this information. #3299

  • Specified UTF8-encoding in calls of open(). #3137

  • Fix a harmless warning from CMake 3.21 with the classic Python discovery. #3220

  • Eigen repo and version can now be specified as cmake options. #3324

Backend and tidying up:

  • Reduced thread-local storage required for keeping alive temporary data for type conversion to one key per ABI version, rather than one key per extension module. This makes the total thread-local storage required by pybind11 2 keys per ABI version. #3275

  • Optimize NumPy array construction with additional moves. #3183

  • Conversion to std::string and std::string_view now avoids making an extra copy of the data on Python >= 3.3. #3257

  • Remove const modifier from certain C++ methods on Python collections (list, set, dict) such as (clear(), append(), insert(), etc…) and annotated them with py-non-const.

  • Enable readability clang-tidy-const-return and remove useless consts. #3254 #3194

  • The clang-tidy google-explicit-constructor option was enabled. #3250

  • Mark a pytype move constructor as noexcept (perf). #3236

  • Enable clang-tidy check to guard against inheritance slicing. #3210

  • Legacy warning suppression pragma were removed from eigen.h. On Unix platforms, please use -isystem for Eigen include directories, to suppress compiler warnings originating from Eigen headers. Note that CMake does this by default. No adjustments are needed for Windows. #3198

  • Format pybind11 with isort consistent ordering of imports #3195

  • The warnings-suppression “pragma clamp” at the top/bottom of pybind11 was removed, clearing the path to refactoring and IWYU cleanup. #3186

  • Enable most bugprone checks in clang-tidy and fix the found potential bugs and poor coding styles. #3166

  • Add clang-tidy-readability rules to make boolean casts explicit improving code readability. Also enabled other misc and readability clang-tidy checks. #3148

  • Move object in .pop() for list. #3116

v2.7.1 (Aug 3, 2021)#

Minor missing functionality added:

  • Allow Python builtins to be used as callbacks in CPython. #1413

Bug fixes:

  • Fix regression in CMake Python package config: improper use of absolute path. #3144

  • Fix Mingw64 and add to the CI testing matrix. #3132

  • Specified UTF8-encoding in calls of open(). #3137

  • Add clang-tidy-readability rules to make boolean casts explicit improving code readability. Also enabled other misc and readability clang-tidy checks. #3148

  • Move object in .pop() for list. #3116

Backend and tidying up:

v2.7.0 (Jul 16, 2021)#

New features:

  • Enable py::implicitly_convertible<py::none, ...> for py::class_-wrapped types. #3059

  • Allow function pointer extraction from overloaded functions. #2944

  • NumPy: added .char_() to type which gives the NumPy public char result, which also distinguishes types by bit length (unlike .kind()). #2864

  • Add pybind11::bytearray to manipulate bytearray similar to bytes. #2799

  • pybind11/stl/filesystem.h registers a type caster that, on C++17/Python 3.6+, converts std::filesystem::path to pathlib.Path and any os.PathLike to std::filesystem::path. #2730

  • A PYBIND11_VERSION_HEX define was added, similar to PY_VERSION_HEX. #3120


  • py::str changed to exclusively hold PyUnicodeObject. Previously py::str could also hold bytes, which is probably surprising, was never documented, and can mask bugs (e.g. accidental use of py::str instead of py::bytes). #2409

  • Add a safety guard to ensure that the Python GIL is held when C++ calls back into Python via object_api<>::operator() (e.g. py::function __call__). (This feature is available for Python 3.6+ only.) #2919

  • Catch a missing self argument in calls to __init__(). #2914

  • Use std::string_view if available to avoid a copy when passing an object to a std::ostream. #3042

  • An important warning about thread safety was added to the iostream.h documentation; attempts to make py::scoped_ostream_redirect thread safe have been removed, as it was only partially effective. #2995


  • Performance: avoid unnecessary strlen calls. #3058

  • Fix auto-generated documentation string when using const T in pyarray_t. #3020

  • Unify error messages thrown by simple_collector/unpacking_collector. #3013

  • pybind11::builtin_exception is now explicitly exported, which means the types included/defined in different modules are identical, and exceptions raised in different modules can be caught correctly. The documentation was updated to explain that custom exceptions that are used across module boundaries need to be explicitly exported as well. #2999

  • Fixed exception when printing UTF-8 to a scoped_ostream_redirect. #2982

  • Pickle support enhancement: setstate implementation will attempt to setattr __dict__ only if the unpickled dict object is not empty, to not force use of py::dynamic_attr() unnecessarily. #2972

  • Allow negative timedelta values to roundtrip. #2870

  • Fix unchecked errors could potentially swallow signals/other exceptions. #2863

  • Add null pointer check with std::localtime. #2846

  • Fix the weakref constructor from py::object to create a new weakref on conversion. #2832

  • Avoid relying on exceptions in C++17 when getting a shared_ptr holder from a shared_from_this class. #2819

  • Allow the codec’s exception to be raised instead of RuntimeError when casting from py::str to std::string. #2903

Build system improvements:

  • In, test for platforms that have some multiprocessing features but lack semaphores, which ParallelCompile requires. #3043

  • Fix pybind11_INCLUDE_DIR in case CMAKE_INSTALL_INCLUDEDIR is absolute. #3005

  • Fix bug not respecting WITH_SOABI or WITHOUT_SOABI to CMake. #2938

  • Fix the default Pybind11Extension compilation flags with a Mingw64 python. #2921

  • Clang on Windows: do not pass /MP (ignored flag). #2824

  • pybind11.setup_helpers.intree_extensions can be used to generate Pybind11Extension instances from cpp files placed in the Python package source tree. #2831

Backend and tidying up:

  • Enable clang-tidy performance, readability, and modernization checks throughout the codebase to enforce best coding practices. #3046, #3049, #3051, #3052, #3080, and #3094

  • Checks for common misspellings were added to the pre-commit hooks. #3076

  • Changed Werror to stricter Werror-all for Intel compiler and fixed minor issues. #2948

  • Fixed compilation with GCC < 5 when the user defines _GLIBCXX_USE_CXX11_ABI. #2956

  • Added nox support for easier local testing and linting of contributions. #3101 and #3121

  • Avoid RTD style issue with docutils 0.17+. #3119

  • Support pipx run, such as pipx run pybind11 --include for a quick compile. #3117

v2.6.2 (Jan 26, 2021)#

Minor missing functionality added:

  • enum: add missing Enum.value property. #2739

  • Allow thread termination to be avoided during shutdown for CPython 3.7+ via .disarm for gil_scoped_acquire/gil_scoped_release. #2657

Fixed or improved behavior in a few special cases:

  • Fix bug where the constructor of object subclasses would not throw on being passed a Python object of the wrong type. #2701

  • The type_caster for integers does not convert Python objects with __int__ anymore with noconvert or during the first round of trying overloads. #2698

  • When casting to a C++ integer, __index__ is always called and not considered as conversion, consistent with Python 3.8+. #2801

Build improvements:

  • Setup helpers: extra_compile_args and extra_link_args automatically set by Pybind11Extension are now prepended, which allows them to be overridden by user-set extra_compile_args and extra_link_args. #2808

  • Setup helpers: Don’t trigger unused parameter warning. #2735

  • CMake: Support running with --warn-uninitialized active. #2806

  • CMake: Avoid error if included from two submodule directories. #2804

  • CMake: Fix STATIC / SHARED being ignored in FindPython mode. #2796

  • CMake: Respect the setting for CMAKE_CXX_VISIBILITY_PRESET if defined. #2793

  • CMake: Fix issue with FindPython2/FindPython3 not working with pybind11::embed. #2662

  • CMake: mixing local and installed pybind11’s would prioritize the installed one over the local one (regression in 2.6.0). #2716

Bug fixes:

  • Fixed segfault in multithreaded environments when using scoped_ostream_redirect. #2675

  • Leave docstring unset when all docstring-related options are disabled, rather than set an empty string. #2745

  • The module key in builtins that pybind11 uses to store its internals changed from std::string to a python str type (more natural on Python 2, no change on Python 3). #2814

  • Fixed assertion error related to unhandled (later overwritten) exception in CPython 3.8 and 3.9 debug builds. #2685

  • Fix py::gil_scoped_acquire assert with CPython 3.9 debug build. #2683

  • Fix issue with a test failing on pytest 6.2. #2741

Warning fixes:

  • Fix warning modifying constructor parameter ‘flag’ that shadows a field of ‘set_flag’ [-Wshadow-field-in-constructor-modified]. #2780

  • Suppressed some deprecation warnings about old-style __init__/__setstate__ in the tests. #2759

Valgrind work:

  • Fix invalid access when calling a pybind11 __init__ on a non-pybind11 class instance. #2755

  • Fixed various minor memory leaks in pybind11’s test suite. #2758

  • Resolved memory leak in cpp_function initialization when exceptions occurred. #2756

  • Added a Valgrind build, checking for leaks and memory-related UB, to CI. #2746

Compiler support:

  • Intel compiler was not activating C++14 support due to a broken define. #2679

  • Support ICC and NVIDIA HPC SDK in C++17 mode. #2729

  • Support Intel OneAPI compiler (ICC 20.2) and add to CI. #2573

v2.6.1 (Nov 11, 2020)#

  • py::exec, py::eval, and py::eval_file now add the builtins module as "__builtins__" to their globals argument, better matching exec and eval in pure Python. #2616

  • setup_helpers will no longer set a minimum macOS version higher than the current version. #2622

  • Allow deleting static properties. #2629

  • Seal a leak in def_buffer, cleaning up the capture object after the class_ object goes out of scope. #2634

  • pybind11_INCLUDE_DIRS was incorrect, potentially causing a regression if it was expected to include PYTHON_INCLUDE_DIRS (please use targets instead). #2636

  • Added parameter names to the py::enum_ constructor and methods, avoiding arg0 in the generated docstrings. #2637

  • Added needs_recompile optional function to the ParallelCompiler helper, to allow a recompile to be skipped based on a user-defined function. #2643

v2.6.0 (Oct 21, 2020)#

See v2.6 for help upgrading to the new version.

New features:

  • Keyword-only arguments supported in Python 2 or 3 with py::kw_only(). #2100

  • Positional-only arguments supported in Python 2 or 3 with py::pos_only(). #2459

  • py::is_final() class modifier to block subclassing (CPython only). #2151

  • Added py::prepend(), allowing a function to be placed at the beginning of the overload chain. #1131

  • Access to the type object now provided with py::type::of<T>() and py::type::of(h). #2364

  • Perfect forwarding support for methods. #2048

  • Added py::error_already_set::discard_as_unraisable(). #2372

  • py::hash is now public. #2217

  • py::class_<union_type> is now supported. Note that writing to one data member of the union and reading another (type punning) is UB in C++. Thus pybind11-bound enums should never be used for such conversions. #2320.

  • Classes now check local scope when registering members, allowing a subclass to have a member with the same name as a parent (such as an enum). #2335

Code correctness features:

  • Error now thrown when __init__ is forgotten on subclasses. #2152

  • Throw error if conversion to a pybind11 type if the Python object isn’t a valid instance of that type, such as py::bytes(o) when py::object o isn’t a bytes instance. #2349

  • Throw if conversion to str fails. #2477

API changes:

  • py::module was renamed py::module_ to avoid issues with C++20 when used unqualified, but an alias py::module is provided for backward compatibility. #2489

  • Public constructors for py::module_ have been deprecated; please use pybind11::module_::create_extension_module if you were using the public constructor (fairly rare after PYBIND11_MODULE was introduced). #2552

  • PYBIND11_OVERLOAD* macros and get_overload function replaced by correctly-named PYBIND11_OVERRIDE* and get_override, fixing inconsistencies in the presence of a closing ; in these macros. get_type_overload is deprecated. #2325

Packaging / building improvements:

  • The Python package was reworked to be more powerful and useful. #2433

    • Building with setuptools is easier thanks to a new pybind11.setup_helpers module, which provides utilities to use setuptools with pybind11. It can be used via PEP 518, setup_requires, or by directly importing or copying into your project.

    • CMake configuration files are now included in the Python package. Use pybind11.get_cmake_dir() or python -m pybind11 --cmakedir to get the directory with the CMake configuration files, or include the site-packages location in your CMAKE_MODULE_PATH. Or you can use the new pybind11[global] extra when you install pybind11, which installs the CMake files and headers into your base environment in the standard location.

    • pybind11-config is another way to write python -m pybind11 if you have your PATH set up.

    • Added external typing support to the helper module, code from import pybind11 can now be type checked. #2588

  • Minimum CMake required increased to 3.4. #2338 and #2370

    • Full integration with CMake’s C++ standard system and compile features replaces PYBIND11_CPP_STANDARD.

    • Generated config file is now portable to different Python/compiler/CMake versions.

    • Virtual environments prioritized if PYTHON_EXECUTABLE is not set (venv, virtualenv, and conda) (similar to the new FindPython mode).

    • Other CMake features now natively supported, like CMAKE_INTERPROCEDURAL_OPTIMIZATION, set(CMAKE_CXX_VISIBILITY_PRESET hidden).

    • CUDA as a language is now supported.

    • Helper functions pybind11_strip, pybind11_extension, pybind11_find_import added, see CMake helpers.

    • Optional FindPython mode and Advanced: NOPYTHON mode with CMake. #2370

  • Uninstall target added. #2265 and #2346

  • pybind11_add_module() now accepts an optional OPT_SIZE flag that switches the binding target to size-based optimization if the global build type can not always be fixed to MinSizeRel (except in debug mode, where optimizations remain disabled). MinSizeRel or this flag reduces binary size quite substantially (~25% on some platforms). #2463

Smaller or developer focused features and fixes:

  • Moved to a new repo, pybind11-mkdoc. There are no longer submodules in the main repo.

  • py::memoryview segfault fix and update, with new py::memoryview::from_memory in Python 3, and documentation. #2223

  • Fix for buffer_info on Python 2. #2503

  • If __eq__ defined but not __hash__, __hash__ is now set to None. #2291

  • py::ellipsis now also works on Python 2. #2360

  • Pointer to std::tuple & std::pair supported in cast. #2334

  • Small fixes in NumPy support. py::array now uses py::ssize_t as first argument type. #2293

  • Added missing signature for py::array. #2363

  • unchecked_mutable_reference has access to operator () and [] when const. #2514

  • py::vectorize is now supported on functions that return void. #1969

  • py::capsule supports get_pointer and set_pointer. #1131

  • Fix crash when different instances share the same pointer of the same type. #2252

  • Fix for py::len not clearing Python’s error state when it fails and throws. #2575

  • Bugfixes related to more extensive testing, new GitHub Actions CI. #2321

  • Bug in timezone issue in Eastern hemisphere midnight fixed. #2438

  • std::chrono::time_point now works when the resolution is not the same as the system. #2481

  • Bug fixed where py::array_t could accept arrays that did not match the requested ordering. #2484

  • Avoid a segfault on some compilers when types are removed in Python. #2564

  • py::arg::none() is now also respected when passing keyword arguments. #2611

  • PyPy fixes, PyPy 7.3.x now supported, including PyPy3. (Known issue with PyPy2 and Windows #2596). #2146

  • CPython 3.9.0 workaround for undefined behavior (macOS segfault). #2576

  • CPython 3.9 warning fixes. #2253

  • Improved C++20 support, now tested in CI. #2489 #2599

  • Improved but still incomplete debug Python interpreter support. #2025

  • NVCC (CUDA 11) now supported and tested in CI. #2461

  • NVIDIA PGI compilers now supported and tested in CI. #2475

  • At least Intel 18 now explicitly required when compiling with Intel. #2577

  • Extensive style checking in CI, with pre-commit support. Code modernization, checked by clang-tidy.

  • Expanded docs, including new main page, new installing section, and CMake helpers page, along with over a dozen new sections on existing pages.

  • In GitHub, new docs for contributing and new issue templates.

v2.5.0 (Mar 31, 2020)#

  • Use C++17 fold expressions in type casters, if available. This can improve performance during overload resolution when functions have multiple arguments. #2043.

  • Changed include directory resolution in pybind11/ and installation in This fixes a number of open issues where pybind11 headers could not be found in certain environments. #1995.

  • C++20 char8_t and u8string support. #2026.

  • CMake: search for Python 3.9. bb9c91.

  • Fixes for MSYS-based build environments. #2087, #2053.

  • STL bindings for std::vector<...>::clear. #2074.

  • Read-only flag for py::buffer. #1466.

  • Exception handling during module initialization. bf2b031.

  • Support linking against a CPython debug build. #2025.

  • Fixed issues involving the availability and use of aligned new and delete. #1988, 759221.

  • Fixed a resource leak upon interpreter shutdown. #2020.

  • Fixed error handling in the boolean caster. #1976.

v2.4.3 (Oct 15, 2019)#

  • Adapt pybind11 to a C API convention change in Python 3.8. #1950.

v2.4.2 (Sep 21, 2019)#

  • Replaced usage of a C++14 only construct. #1929.

  • Made an ifdef future-proof for Python >= 4. f3109d.

v2.4.1 (Sep 20, 2019)#

  • Fixed a problem involving implicit conversion from enumerations to integers on Python 3.8. #1780.

v2.4.0 (Sep 19, 2019)#

  • Try harder to keep pybind11-internal data structures separate when there are potential ABI incompatibilities. Fixes crashes that occurred when loading multiple pybind11 extensions that were e.g. compiled by GCC (libstdc++) and Clang (libc++). #1588 and c9f5a.

  • Added support for __await__, __aiter__, and __anext__ protocols. #1842.

  • pybind11_add_module(): don’t strip symbols when compiling in RelWithDebInfo mode. #1980.

  • enum_: Reproduce Python behavior when comparing against invalid values (e.g. None, strings, etc.). Add back support for __invert__(). #1912, #1907.

  • List insertion operation for py::list. Added .empty() to all collection types. Added py::set::contains() and py::dict::contains(). #1887, #1884, #1888.

  • py::details::overload_cast_impl is available in C++11 mode, can be used like overload_cast with an additional set of parentheses. #1581.

  • Fixed get_include() on Conda. #1877.

  • stl_bind.h: negative indexing support. #1882.

  • Minor CMake fix to add MinGW compatibility. #1851.

  • GIL-related fixes. #1836, 8b90b.

  • Other very minor/subtle fixes and improvements. #1329, #1910, #1863, #1847, #1890, #1860, #1848, #1821, #1837, #1833, #1748, #1852.

v2.3.0 (June 11, 2019)#

  • Significantly reduced module binary size (10-20%) when compiled in C++11 mode with GCC/Clang, or in any mode with MSVC. Function signatures are now always precomputed at compile time (this was previously only available in C++14 mode for non-MSVC compilers). #934.

  • Add basic support for tag-based static polymorphism, where classes provide a method to returns the desired type of an instance. #1326.

  • Python type wrappers (py::handle, py::object, etc.) now support map Python’s number protocol onto C++ arithmetic operators such as operator+, operator/=, etc. #1511.

  • A number of improvements related to enumerations:

    1. The enum_ implementation was rewritten from scratch to reduce code bloat. Rather than instantiating a full implementation for each enumeration, most code is now contained in a generic base class. #1511.

    2. The value() method of py::enum_ now accepts an optional docstring that will be shown in the documentation of the associated enumeration. #1160.

    3. check for already existing enum value and throw an error if present. #1453.

  • Support for over-aligned type allocation via C++17’s aligned new statement. #1582.

  • Added py::ellipsis() method for slicing of multidimensional NumPy arrays #1502.

  • Numerous Improvements to the script for extracting documentation from C++ header files. #1788.

  • pybind11_add_module(): allow including Python as a SYSTEM include path. #1416.

  • pybind11/stl.h does not convert strings to vector<string> anymore. #1258.

  • Mark static methods as such to fix auto-generated Sphinx documentation. #1732.

  • Re-throw forced unwind exceptions (e.g. during pthread termination). #1208.

  • Added __contains__ method to the bindings of maps (std::map, std::unordered_map). #1767.

  • Improvements to gil_scoped_acquire. #1211.

  • Type caster support for std::deque<T>. #1609.

  • Support for std::unique_ptr holders, whose deleters differ between a base and derived class. #1353.

  • Construction of STL array/vector-like data structures from iterators. Added an extend() operation. #1709,

  • CMake build system improvements for projects that include non-C++ files (e.g. plain C, CUDA) in pybind11_add_module et al. #1678.

  • Fixed asynchronous invocation and deallocation of Python functions wrapped in std::function. #1595.

  • Fixes regarding return value policy propagation in STL type casters. #1603.

  • Fixed scoped enum comparisons. #1571.

  • Fixed iostream redirection for code that releases the GIL. #1368,

  • A number of CI-related fixes. #1757, #1744, #1670.

v2.2.4 (September 11, 2018)#

  • Use new Python 3.7 Thread Specific Storage (TSS) implementation if available. #1454, #1517.

  • Fixes for newer MSVC versions and C++17 mode. #1347, #1462.

  • Propagate return value policies to type-specific casters when casting STL containers. #1455.

  • Allow ostream-redirection of more than 1024 characters. #1479.

  • Set Py_DEBUG define when compiling against a debug Python build. #1438.

  • Untangle integer logic in number type caster to work for custom types that may only be castable to a restricted set of builtin types. #1442.

  • CMake build system: Remember Python version in cache file. #1434.

  • Fix for custom smart pointers: use std::addressof to obtain holder address instead of operator&. #1435.

  • Properly report exceptions thrown during module initialization. #1362.

  • Fixed a segmentation fault when creating empty-shaped NumPy array. #1371.

  • The version of Intel C++ compiler must be >= 2017, and this is now checked by the header files. #1363.

  • A few minor typo fixes and improvements to the test suite, and patches that silence compiler warnings.

  • Vectors now support construction from generators, as well as extend() from a list or generator. #1496.

v2.2.3 (April 29, 2018)#

  • The pybind11 header location detection was replaced by a new implementation that no longer depends on pip internals (the recently released pip 10 has restricted access to this API). #1190.

  • Small adjustment to an implementation detail to work around a compiler segmentation fault in Clang 3.3/3.4. #1350.

  • The minimal supported version of the Intel compiler was >= 17.0 since pybind11 v2.1. This check is now explicit, and a compile-time error is raised if the compiler meet the requirement. #1363.

  • Fixed an endianness-related fault in the test suite. #1287.

v2.2.2 (February 7, 2018)#

  • Fixed a segfault when combining embedded interpreter shutdown/reinitialization with external loaded pybind11 modules. #1092.

  • Eigen support: fixed a bug where Nx1/1xN numpy inputs couldn’t be passed as arguments to Eigen vectors (which for Eigen are simply compile-time fixed Nx1/1xN matrices). #1106.

  • Clarified to license by moving the licensing of contributions from LICENSE into the licensing of contributions is not actually part of the software license as distributed. This isn’t meant to be a substantial change in the licensing of the project, but addresses concerns that the clause made the license non-standard. #1109.

  • Fixed a regression introduced in 2.1 that broke binding functions with lvalue character literal arguments. #1128.

  • MSVC: fix for compilation failures under /permissive-, and added the flag to the appveyor test suite. #1155.

  • Fixed __qualname__ generation, and in turn, fixes how class names (especially nested class names) are shown in generated docstrings. #1171.

  • Updated the FAQ with a suggested project citation reference. #1189.

  • Added fixes for deprecation warnings when compiled under C++17 with -Wdeprecated turned on, and add -Wdeprecated to the test suite compilation flags. #1191.

  • Fixed outdated PyPI URLs in #1213.

  • Fixed a refcount leak for arguments that end up in a py::args argument for functions with both fixed positional and py::args arguments. #1216.

  • Fixed a potential segfault resulting from possible premature destruction of py::args/py::kwargs arguments with overloaded functions. #1223.

  • Fixed del map[item] for a stl_bind.h bound stl map. #1229.

  • Fixed a regression from v2.1.x where the aggregate initialization could unintentionally end up at a constructor taking a templated std::initializer_list<T> argument. #1249.

  • Fixed an issue where calling a function with a keep_alive policy on the same nurse/patient pair would cause the internal patient storage to needlessly grow (unboundedly, if the nurse is long-lived). #1251.

  • Various other minor fixes.

v2.2.1 (September 14, 2017)#

  • Added py::module_::reload() member function for reloading a module. #1040.

  • Fixed a reference leak in the number converter. #1078.

  • Fixed compilation with Clang on host GCC < 5 (old libstdc++ which isn’t fully C++11 compliant). #1062.

  • Fixed a regression where the automatic std::vector<bool> caster would fail to compile. The same fix also applies to any container which returns element proxies instead of references. #1053.

  • Fixed a regression where the py::keep_alive policy could not be applied to constructors. #1065.

  • Fixed a nullptr dereference when loading a py::module_local type that’s only registered in an external module. #1058.

  • Fixed implicit conversion of accessors to types derived from py::object. #1076.

  • The name in PYBIND11_MODULE(name, variable) can now be a macro. #1082.

  • Relaxed overly strict py::pickle() check for matching get and set types. #1064.

  • Conversion errors now try to be more informative when it’s likely that a missing header is the cause (e.g. forgetting <pybind11/stl.h>). #1077.

v2.2.0 (August 31, 2017)#

  • Support for embedding the Python interpreter. See the documentation page for a full overview of the new features. #774, #889, #892, #920.

    #include <pybind11/embed.h>
    namespace py = pybind11;
    int main() {
        py::scoped_interpreter guard{}; // start the interpreter and keep it alive
        py::print("Hello, World!"); // use the Python API
  • Support for inheriting from multiple C++ bases in Python. #693.

    from cpp_module import CppBase1, CppBase2
    class PyDerived(CppBase1, CppBase2):
        def __init__(self):
            CppBase1.__init__(self)  # C++ bases must be initialized explicitly
  • PYBIND11_MODULE is now the preferred way to create module entry points. PYBIND11_PLUGIN is deprecated. See Macros for details. #879.

    // new
    PYBIND11_MODULE(example, m) {
        m.def("add", [](int a, int b) { return a + b; });
    // old
    PYBIND11_PLUGIN(example) {
        py::module m("example");
        m.def("add", [](int a, int b) { return a + b; });
        return m.ptr();
  • pybind11’s headers and build system now more strictly enforce hidden symbol visibility for extension modules. This should be seamless for most users, but see the Upgrade guide if you use a custom build system. #995.

  • Support for py::module_local types which allow multiple modules to export the same C++ types without conflicts. This is useful for opaque types like std::vector<int>. py::bind_vector and py::bind_map now default to py::module_local if their elements are builtins or local types. See Module-local class bindings for details. #949, #981, #995, #997.

  • Custom constructors can now be added very easily using lambdas or factory functions which return a class instance by value, pointer or holder. This supersedes the old placement-new __init__ technique. See Custom constructors for details. #805, #1014.

    struct Example {
    py::class_<Example>(m, "Example")
        .def(py::init<std::string>()) // existing constructor
        .def(py::init([](int n) { // custom constructor
            return std::make_unique<Example>(std::to_string(n));
  • Similarly to custom constructors, pickling support functions are now bound using the py::pickle() adaptor which improves type safety. See the Upgrade guide and Pickling support for details. #1038.

  • Builtin support for converting C++17 standard library types and general conversion improvements:

    1. C++17 std::variant is supported right out of the box. C++11/14 equivalents (e.g. boost::variant) can also be added with a simple user-defined specialization. See C++17 library containers for details. #811, #845, #989.

    2. Out-of-the-box support for C++17 std::string_view. #906.

    3. Improved compatibility of the builtin optional converter. #874.

    4. The bool converter now accepts numpy.bool_ and types which define __bool__ (Python 3.x) or __nonzero__ (Python 2.7). #925.

    5. C++-to-Python casters are now more efficient and move elements out of rvalue containers whenever possible. #851, #936, #938.

    6. Fixed bytes to std::string/char* conversion on Python 3. #817.

    7. Fixed lifetime of temporary C++ objects created in Python-to-C++ conversions. #924.

  • Scope guard call policy for RAII types, e.g. py::call_guard<py::gil_scoped_release>(), py::call_guard<py::scoped_ostream_redirect>(). See Additional call policies for details. #740.

  • Utility for redirecting C++ streams to Python (e.g. std::cout -> sys.stdout). Scope guard py::scoped_ostream_redirect in C++ and a context manager in Python. See Capturing standard output from ostream. #1009.

  • Improved handling of types and exceptions across module boundaries. #915, #951, #995.

  • Fixed destruction order of py::keep_alive nurse/patient objects in reference cycles. #856.

  • NumPy and buffer protocol related improvements:

    1. Support for negative strides in Python buffer objects/numpy arrays. This required changing integers from unsigned to signed for the related C++ APIs. Note: If you have compiler warnings enabled, you may notice some new conversion warnings after upgrading. These can be resolved with static_cast. #782.

    2. Support std::complex and arrays inside PYBIND11_NUMPY_DTYPE. #831, #832.

    3. Support for constructing py::buffer_info and py::arrays using arbitrary containers or iterators instead of requiring a std::vector. #788, #822, #860.

    4. Explicitly check numpy version and require >= 1.7.0. #819.

  • Support for allowing/prohibiting None for specific arguments and improved None overload resolution order. See Allow/Prohibiting None arguments for details. #843. #859.

  • Added py::exec() as a shortcut for py::eval<py::eval_statements>() and support for C++11 raw string literals as input. See Evaluating Python expressions from strings and files. #766, #827.

  • py::vectorize() ignores non-vectorizable arguments and supports member functions. #762.

  • Support for bound methods as callbacks (pybind11/functional.h). #815.

  • Allow aliasing pybind11 methods: cls.attr("foo") = cls.attr("bar"). #802.

  • Don’t allow mixed static/non-static overloads. #804.

  • Fixed overriding static properties in derived classes. #784.

  • Added support for write only properties. #1144.

  • Improved deduction of member functions of a derived class when its bases aren’t registered with pybind11. #855.

    struct Base {
        int foo() { return 42; }
    struct Derived : Base {}
    // Now works, but previously required also binding `Base`
    py::class_<Derived>(m, "Derived")
        .def("foo", &Derived::foo); // function is actually from `Base`
  • The implementation of py::init<> now uses C++11 brace initialization syntax to construct instances, which permits binding implicit constructors of aggregate types. #1015.

    struct Aggregate {
        int a;
        std::string b;
    py::class_<Aggregate>(m, "Aggregate")
        .def(py::init<int, const std::string &>());
  • Fixed issues with multiple inheritance with offset base/derived pointers. #812, #866, #960.

  • Fixed reference leak of type objects. #1030.

  • Improved support for the /std:c++14 and /std:c++latest modes on MSVC 2017. #841, #999.

  • Fixed detection of private operator new on MSVC. #893, #918.

  • Intel C++ compiler compatibility fixes. #937.

  • Fixed implicit conversion of py::enum_ to integer types on Python 2.7. #821.

  • Added py::hash to fetch the hash value of Python objects, and .def(hash(py::self)) to provide the C++ std::hash as the Python __hash__ method. #1034.

  • Fixed __truediv__ on Python 2 and __itruediv__ on Python 3. #867.

  • py::capsule objects now support the name attribute. This is useful for interfacing with scipy.LowLevelCallable. #902.

  • Fixed py::make_iterator’s __next__() for past-the-end calls. #897.

  • Added error_already_set::matches() for checking Python exceptions. #772.

  • Deprecated py::error_already_set::clear(). It’s no longer needed following a simplification of the py::error_already_set class. #954.

  • Deprecated py::handle::operator==() in favor of py::handle::is() #825.

  • Deprecated py::object::borrowed/py::object::stolen. Use py::object::borrowed_t{}/py::object::stolen_t{} instead. #771.

  • Changed internal data structure versioning to avoid conflicts between modules compiled with different revisions of pybind11. #1012.

  • Additional compile-time and run-time error checking and more informative messages. #786, #794, #803.

  • Various minor improvements and fixes. #764, #791, #795, #840, #844, #846, #849, #858, #862, #871, #872, #881, #888, #899, #928, #931, #944, #950, #952, #962, #965, #970, #978, #979, #986, #1020, #1027, #1037.

  • Testing improvements. #798, #882, #898, #900, #921, #923, #963.

v2.1.1 (April 7, 2017)#

  • Fixed minimum version requirement for MSVC 2015u3 #773.

v2.1.0 (March 22, 2017)#

  • pybind11 now performs function overload resolution in two phases. The first phase only considers exact type matches, while the second allows for implicit conversions to take place. A special noconvert() syntax can be used to completely disable implicit conversions for specific arguments. #643, #634, #650.

  • Fixed a regression where static properties no longer worked with classes using multiple inheritance. The py::metaclass attribute is no longer necessary (and deprecated as of this release) when binding classes with static properties. #679,

  • Classes bound using pybind11 can now use custom metaclasses. #679,

  • py::args and py::kwargs can now be mixed with other positional arguments when binding functions using pybind11. #611.

  • Improved support for C++11 unicode string and character types; added extensive documentation regarding pybind11’s string conversion behavior. #624, #636, #715.

  • pybind11 can now avoid expensive copies when converting Eigen arrays to NumPy arrays (and vice versa). #610.

  • The “fast path” in py::vectorize now works for any full-size group of C or F-contiguous arrays. The non-fast path is also faster since it no longer performs copies of the input arguments (except when type conversions are necessary). #610.

  • Added fast, unchecked access to NumPy arrays via a proxy object. #746.

  • Transparent support for class-specific operator new and operator delete implementations. #755.

  • Slimmer and more efficient STL-compatible iterator interface for sequence types. #662.

  • Improved custom holder type support. #607.

  • nullptr to None conversion fixed in various builtin type casters. #732.

  • enum_ now exposes its members via a special __members__ attribute. #666.

  • std::vector bindings created using stl_bind.h can now optionally implement the buffer protocol. #488.

  • Automated C++ reference documentation using doxygen and breathe. #598.

  • Added minimum compiler version assertions. #727.

  • Improved compatibility with C++1z. #677.

  • Improved py::capsule API. Can be used to implement cleanup callbacks that are involved at module destruction time. #752.

  • Various minor improvements and fixes. #595, #588, #589, #603, #619, #648, #695, #720, #723, #729, #724, #742, #753.

v2.0.1 (Jan 4, 2017)#

  • Fix pointer to reference error in type_caster on MSVC #583.

  • Fixed a segmentation in the test suite due to a typo cd7eac.

v2.0.0 (Jan 1, 2017)#

  • Fixed a reference counting regression affecting types with custom metaclasses (introduced in v2.0.0-rc1). #571.

  • Quenched a CMake policy warning. #570.

v2.0.0-rc1 (Dec 23, 2016)#

The pybind11 developers are excited to issue a release candidate of pybind11 with a subsequent v2.0.0 release planned in early January next year.

An incredible amount of effort by went into pybind11 over the last ~5 months, leading to a release that is jam-packed with exciting new features and numerous usability improvements. The following list links PRs or individual commits whenever applicable.

Happy Christmas!

  • Support for binding C++ class hierarchies that make use of multiple inheritance. #410.

  • PyPy support: pybind11 now supports nightly builds of PyPy and will interoperate with the future 5.7 release. No code changes are necessary, everything “just” works as usual. Note that we only target the Python 2.7 branch for now; support for 3.x will be added once its cpyext extension support catches up. A few minor features remain unsupported for the time being (notably dynamic attributes in custom types). #527.

  • Significant work on the documentation – in particular, the monolithic advanced.rst file was restructured into a easier to read hierarchical organization. #448.

  • Many NumPy-related improvements:

    1. Object-oriented API to access and modify NumPy ndarray instances, replicating much of the corresponding NumPy C API functionality. #402.

    2. NumPy array dtype array descriptors are now first-class citizens and are exposed via a new class py::dtype.

    3. Structured dtypes can be registered using the PYBIND11_NUMPY_DTYPE() macro. Special array constructors accepting dtype objects were also added.

      One potential caveat involving this change: format descriptor strings should now be accessed via format_descriptor::format() (however, for compatibility purposes, the old syntax format_descriptor::value will still work for non-structured data types). #308.

    4. Further improvements to support structured dtypes throughout the system. #472, #474, #459, #453, #452, and #505.

    5. Fast access operators. #497.

    6. Constructors for arrays whose storage is owned by another object. #440.

    7. Added constructors for array and array_t explicitly accepting shape and strides; if strides are not provided, they are deduced assuming C-contiguity. Also added simplified constructors for 1-dimensional case.

    8. Added buffer/NumPy support for char[N] and std::array<char, N> types.

    9. Added memoryview wrapper type which is constructible from buffer_info.

  • Eigen: many additional conversions and support for non-contiguous arrays/slices. #427, #315, #316, #312, and #267

  • Incompatible changes in class_<...>::class_():

    1. Declarations of types that provide access via the buffer protocol must now include the py::buffer_protocol() annotation as an argument to the class_ constructor.

    2. Declarations of types that require a custom metaclass (i.e. all classes which include static properties via commands such as def_readwrite_static()) must now include the py::metaclass() annotation as an argument to the class_ constructor.

      These two changes were necessary to make type definitions in pybind11 future-proof, and to support PyPy via its cpyext mechanism. #527.

    3. This version of pybind11 uses a redesigned mechanism for instantiating trampoline classes that are used to override virtual methods from within Python. This led to the following user-visible syntax change: instead of



      py::class_<MyClass, TrampolineClass>("MyClass")

      Importantly, both the original and the trampoline class are now specified as an arguments (in arbitrary order) to the py::class_ template, and the alias<..>() call is gone. The new scheme has zero overhead in cases when Python doesn’t override any functions of the underlying C++ class. rev. 86d825.

  • Added eval and eval_file functions for evaluating expressions and statements from a string or file. rev. 0d3fc3.

  • pybind11 can now create types with a modifiable dictionary. #437 and #444.

  • Support for translation of arbitrary C++ exceptions to Python counterparts. #296 and #273.

  • Report full backtraces through mixed C++/Python code, better reporting for import errors, fixed GIL management in exception processing. #537, #494, rev. e72d95, and rev. 099d6e.

  • Support for bit-level operations, comparisons, and serialization of C++ enumerations. #503, #508, #380, #309. #311.

  • The class_ constructor now accepts its template arguments in any order. #385.

  • Attribute and item accessors now have a more complete interface which makes it possible to chain attributes as in obj.attr("a")[key].attr("b").attr("method")(1, 2, 3). #425.

  • Major redesign of the default and conversion constructors in pytypes.h. #464.

  • Added built-in support for std::shared_ptr holder type. It is no longer necessary to to include a declaration of the form PYBIND11_DECLARE_HOLDER_TYPE(T, std::shared_ptr<T>) (though continuing to do so won’t cause an error). #454.

  • New py::overload_cast casting operator to select among multiple possible overloads of a function. An example:

    py::class_<Pet>(m, "Pet")
        .def("set", py::overload_cast<int>(&Pet::set), "Set the pet's age")
        .def("set", py::overload_cast<const std::string &>(&Pet::set), "Set the pet's name");

    This feature only works on C++14-capable compilers. #541.

  • C++ types are automatically cast to Python types, e.g. when assigning them as an attribute. For instance, the following is now legal:

    py::module m = /* ... */
    m.attr("constant") = 123;

    (Previously, a py::cast call was necessary to avoid a compilation error.) #551.

  • Redesigned pytest-based test suite. #321.

  • Instance tracking to detect reference leaks in test suite. #324

  • pybind11 can now distinguish between multiple different instances that are located at the same memory address, but which have different types. #329.

  • Improved logic in move return value policy. #510, #297.

  • Generalized unpacking API to permit calling Python functions from C++ using notation such as foo(a1, a2, *args, "ka"_a=1, "kb"_a=2, **kwargs). #372.

  • py::print() function whose behavior matches that of the native Python print() function. #372.

  • Added py::dict keyword constructor:auto d = dict("number"_a=42, "name"_a="World");. #372.

  • Added py::str::format() method and _s literal: py::str s = "1 + 2 = {}"_s.format(3);. #372.

  • Added py::repr() function which is equivalent to Python’s builtin repr(). #333.

  • Improved construction and destruction logic for holder types. It is now possible to reference instances with smart pointer holder types without constructing the holder if desired. The PYBIND11_DECLARE_HOLDER_TYPE macro now accepts an optional second parameter to indicate whether the holder type uses intrusive reference counting. #533 and #561.

  • Mapping a stateless C++ function to Python and back is now “for free” (i.e. no extra indirections or argument conversion overheads). rev. 954b79.

  • Bindings for std::valarray<T>. #545.

  • Improved support for C++17 capable compilers. #562.

  • Bindings for std::optional<t>. #475, #476, #479, #499, and #501.

  • stl_bind.h: general improvements and support for std::map and std::unordered_map. #490, #282, #235.

  • The std::tuple, std::pair, std::list, and std::vector type casters now accept any Python sequence type as input. rev. 107285.

  • Improved CMake Python detection on multi-architecture Linux. #532.

  • Infrastructure to selectively disable or enable parts of the automatically generated docstrings. #486.

  • reference and reference_internal are now the default return value properties for static and non-static properties, respectively. #473. (the previous defaults were automatic). #473.

  • Support for std::unique_ptr with non-default deleters or no deleter at all (py::nodelete). #384.

  • Deprecated handle::call() method. The new syntax to call Python functions is simply handle(). It can also be invoked explicitly via handle::operator<X>(), where X is an optional return value policy.

  • Print more informative error messages when make_tuple() or cast() fail. #262.

  • Creation of holder types for classes deriving from std::enable_shared_from_this<> now also works for const values. #260.

  • make_iterator() improvements for better compatibility with various types (now uses prefix increment operator); it now also accepts iterators with different begin/end types as long as they are equality comparable. #247.

  • arg() now accepts a wider range of argument types for default values. #244.

  • Support keep_alive where the nurse object may be None. #341.

  • Added constructors for str and bytes from zero-terminated char pointers, and from char pointers and length. Added constructors for str from bytes and for bytes from str, which will perform UTF-8 decoding/encoding as required.

  • Many other improvements of library internals without user-visible changes

1.8.1 (July 12, 2016)#

  • Fixed a rare but potentially very severe issue when the garbage collector ran during pybind11 type creation.

1.8.0 (June 14, 2016)#

  • Redesigned CMake build system which exports a convenient pybind11_add_module function to parent projects.

  • std::vector<> type bindings analogous to Boost.Python’s indexing_suite

  • Transparent conversion of sparse and dense Eigen matrices and vectors (eigen.h)

  • Added an ExtraFlags template argument to the NumPy array_t<> wrapper to disable an enforced cast that may lose precision, e.g. to create overloads for different precisions and complex vs real-valued matrices.

  • Prevent implicit conversion of floating point values to integral types in function arguments

  • Fixed incorrect default return value policy for functions returning a shared pointer

  • Don’t allow registering a type via class_ twice

  • Don’t allow casting a None value into a C++ lvalue reference

  • Fixed a crash in enum_::operator== that was triggered by the help() command

  • Improved detection of whether or not custom C++ types can be copy/move-constructed

  • Extended str type to also work with bytes instances

  • Added a "name"_a user defined string literal that is equivalent to py::arg("name").

  • When specifying function arguments via py::arg, the test that verifies the number of arguments now runs at compile time.

  • Added [[noreturn]] attribute to pybind11_fail() to quench some compiler warnings

  • List function arguments in exception text when the dispatch code cannot find a matching overload

  • Added PYBIND11_OVERLOAD_NAME and PYBIND11_OVERLOAD_PURE_NAME macros which can be used to override virtual methods whose name differs in C++ and Python (e.g. __call__ and operator())

  • Various minor iterator and make_iterator() improvements

  • Transparently support __bool__ on Python 2.x and Python 3.x

  • Fixed issue with destructor of unpickled object not being called

  • Minor CMake build system improvements on Windows

  • New pybind11::args and pybind11::kwargs types to create functions which take an arbitrary number of arguments and keyword arguments

  • New syntax to call a Python function from C++ using *args and *kwargs

  • The functions def_property_* now correctly process docstring arguments (these formerly caused a segmentation fault)

  • Many improvements (enumerations, template arguments, DOC() macro accepts more arguments)

  • Cygwin support

  • Documentation improvements (pickling support, keep_alive, macro usage)

1.7 (April 30, 2016)#

  • Added a new move return value policy that triggers C++11 move semantics. The automatic return value policy falls back to this case whenever a rvalue reference is encountered

  • Significantly more general GIL state routines that are used instead of Python’s troublesome PyGILState_Ensure and PyGILState_Release API

  • Redesign of opaque types that drastically simplifies their usage

  • Extended ability to pass values of type [const] void *

  • keep_alive fix: don’t fail when there is no patient

  • functional.h: acquire the GIL before calling a Python function

  • Added Python RAII type wrappers none and iterable

  • Added *args and *kwargs pass-through parameters to pybind11.get_include() function

  • Iterator improvements and fixes

  • Documentation on return value policies and opaque types improved

1.6 (April 30, 2016)#

1.5 (April 21, 2016)#

  • For polymorphic types, use RTTI to try to return the closest type registered with pybind11

  • Pickling support for serializing and unserializing C++ instances to a byte stream in Python

  • Added a convenience routine make_iterator() which turns a range indicated by a pair of C++ iterators into a iterable Python object

  • Added len() and a variadic make_tuple() function

  • Addressed a rare issue that could confuse the current virtual function dispatcher and another that could lead to crashes in multi-threaded applications

  • Added a get_include() function to the Python module that returns the path of the directory containing the installed pybind11 header files

  • Documentation improvements: import issues, symbol visibility, pickling, limitations

  • Added casting support for std::reference_wrapper<>

1.4 (April 7, 2016)#

  • Transparent type conversion for std::wstring and wchar_t

  • Allow passing nullptr-valued strings

  • Transparent passing of void * pointers using capsules

  • Transparent support for returning values wrapped in std::unique_ptr<>

  • Improved docstring generation for compatibility with Sphinx

  • Nicer debug error message when default parameter construction fails

  • Support for “opaque” types that bypass the transparent conversion layer for STL containers

  • Redesigned type casting interface to avoid ambiguities that could occasionally cause compiler errors

  • Redesigned property implementation; fixes crashes due to an unfortunate default return value policy

  • Anaconda package generation support

1.3 (March 8, 2016)#

  • Added support for the Intel C++ compiler (v15+)

  • Added support for the STL unordered set/map data structures

  • Added support for the STL linked list data structure

  • NumPy-style broadcasting support in pybind11::vectorize

  • pybind11 now displays more verbose error messages when arg::operator=() fails

  • pybind11 internal data structures now live in a version-dependent namespace to avoid ABI issues

  • Many, many bugfixes involving corner cases and advanced usage

1.2 (February 7, 2016)#

  • Optional: efficient generation of function signatures at compile time using C++14

  • Switched to a simpler and more general way of dealing with function default arguments. Unused keyword arguments in function calls are now detected and cause errors as expected

  • New keep_alive call policy analogous to Boost.Python’s with_custodian_and_ward

  • New pybind11::base<> attribute to indicate a subclass relationship

  • Improved interface for RAII type wrappers in pytypes.h

  • Use RAII type wrappers consistently within pybind11 itself. This fixes various potential refcount leaks when exceptions occur

  • Added new bytes RAII type wrapper (maps to string in Python 2.7)

  • Made handle and related RAII classes const correct, using them more consistently everywhere now

  • Got rid of the ugly __pybind11__ attributes on the Python side—they are now stored in a C++ hash table that is not visible in Python

  • Fixed refcount leaks involving NumPy arrays and bound functions

  • Vastly improved handling of shared/smart pointers

  • Removed an unnecessary copy operation in pybind11::vectorize

  • Fixed naming clashes when both pybind11 and NumPy headers are included

  • Added conversions for additional exception types

  • Documentation improvements (using multiple extension modules, smart pointers, other minor clarifications)

  • unified infrastructure for parsing variadic arguments in class_ and cpp_function

  • Fixed license text (was: ZLIB, should have been: 3-clause BSD)

  • Python 3.2 compatibility

  • Fixed remaining issues when accessing types in another plugin module

  • Added enum comparison and casting methods

  • Improved SFINAE-based detection of whether types are copy-constructible

  • Eliminated many warnings about unused variables and the use of offsetof()

  • Support for std::array<> conversions

1.1 (December 7, 2015)#

  • Documentation improvements (GIL, wrapping functions, casting, fixed many typos)

  • Generalized conversion of integer types

  • Improved support for casting function objects

  • Improved support for std::shared_ptr<> conversions

  • Initial support for std::set<> conversions

  • Fixed type resolution issue for types defined in a separate plugin module

  • CMake build system improvements

  • Factored out generic functionality to non-templated code (smaller code size)

  • Added a code size / compile time benchmark vs Boost.Python

  • Added an appveyor CI script

1.0 (October 15, 2015)#

  • Initial release