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.. figure:: https://github.com/pybind/pybind11/raw/master/docs/pybind11-logo.png
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**pybind11 — Seamless operability between C++11 and Python**
2021-07-29 23:10:18 +00:00
|Latest Documentation Status| |Stable Documentation Status| |Gitter chat| |GitHub Discussions| |CI| |Build status|
2020-11-15 17:23:33 +00:00
|Repology| |PyPI package| |Conda-forge| |Python Versions|
`Setuptools example <https://github.com/pybind/python_example>`_
`Scikit-build example <https://github.com/pybind/scikit_build_example>`_
`CMake example <https://github.com/pybind/cmake_example>`_
.. start
.. Note::
This is the pybind11 **smart_holder** branch. Please refer to
``README_smart_holder.rst`` for branch-specific information.
**pybind11** is a lightweight header-only library that exposes C++ types
in Python and vice versa, mainly to create Python bindings of existing
C++ code. Its goals and syntax are similar to the excellent
`Boost.Python <http://www.boost.org/doc/libs/1_58_0/libs/python/doc/>`_
library by David Abrahams: to minimize boilerplate code in traditional
extension modules by inferring type information using compile-time
introspection.
The main issue with Boost.Python—and the reason for creating such a
similar project—is Boost. Boost is an enormously large and complex suite
of utility libraries that works with almost every C++ compiler in
existence. This compatibility has its cost: arcane template tricks and
workarounds are necessary to support the oldest and buggiest of compiler
specimens. Now that C++11-compatible compilers are widely available,
this heavy machinery has become an excessively large and unnecessary
dependency.
Think of this library as a tiny self-contained version of Boost.Python
with everything stripped away that isnt relevant for binding
generation. Without comments, the core header files only require ~4K
lines of code and depend on Python (2.7 or 3.5+, or PyPy) and the C++
standard library. This compact implementation was possible thanks to
some of the new C++11 language features (specifically: tuples, lambda
functions and variadic templates). Since its creation, this library has
grown beyond Boost.Python in many ways, leading to dramatically simpler
binding code in many common situations.
Tutorial and reference documentation is provided at
`pybind11.readthedocs.io <https://pybind11.readthedocs.io/en/latest>`_.
A PDF version of the manual is available
`here <https://pybind11.readthedocs.io/_/downloads/en/latest/pdf/>`_.
And the source code is always available at
`github.com/pybind/pybind11 <https://github.com/pybind/pybind11>`_.
Core features
-------------
pybind11 can map the following core C++ features to Python:
- Functions accepting and returning custom data structures per value,
reference, or pointer
- Instance methods and static methods
- Overloaded functions
- Instance attributes and static attributes
- Arbitrary exception types
- Enumerations
- Callbacks
- Iterators and ranges
- Custom operators
- Single and multiple inheritance
- STL data structures
- Smart pointers with reference counting like ``std::shared_ptr``
- Internal references with correct reference counting
- C++ classes with virtual (and pure virtual) methods can be extended
in Python
Goodies
-------
In addition to the core functionality, pybind11 provides some extra
goodies:
- Python 2.7, 3.5+, and PyPy/PyPy3 7.3 are supported with an
implementation-agnostic interface.
- It is possible to bind C++11 lambda functions with captured
variables. The lambda capture data is stored inside the resulting
Python function object.
- pybind11 uses C++11 move constructors and move assignment operators
whenever possible to efficiently transfer custom data types.
- Its easy to expose the internal storage of custom data types through
Pythons buffer protocols. This is handy e.g. for fast conversion
between C++ matrix classes like Eigen and NumPy without expensive
copy operations.
- pybind11 can automatically vectorize functions so that they are
transparently applied to all entries of one or more NumPy array
arguments.
- Python's slice-based access and assignment operations can be
supported with just a few lines of code.
- Everything is contained in just a few header files; there is no need
to link against any additional libraries.
- Binaries are generally smaller by a factor of at least 2 compared to
equivalent bindings generated by Boost.Python. A recent pybind11
conversion of PyRosetta, an enormous Boost.Python binding project,
`reported <http://graylab.jhu.edu/RosettaCon2016/PyRosetta-4.pdf>`_
a binary size reduction of **5.4x** and compile time reduction by
**5.8x**.
- Function signatures are precomputed at compile time (using
``constexpr``), leading to smaller binaries.
- With little extra effort, C++ types can be pickled and unpickled
similar to regular Python objects.
Supported compilers
-------------------
1. Clang/LLVM 3.3 or newer (for Apple Xcodes clang, this is 5.0.0 or
newer)
2. GCC 4.8 or newer
3. Microsoft Visual Studio 2015 Update 3 or newer
fix: Intel ICC C++17 compatibility (#2729) * CI: Intel icc/icpc via oneAPI Add testing for Intel icc/icpc via the oneAPI images. Intel oneAPI is in a late beta stage, currently shipping oneAPI beta09 with ICC 20.2. CI: Skip Interpreter Tests for Intel Cannot find how to add this, neiter the package `libc6-dev` nor `intel-oneapi-mkl-devel` help when installed to solve this: ``` -- Looking for C++ include pthread.h -- Looking for C++ include pthread.h - not found CMake Error at /__t/cmake/3.18.4/x64/cmake-3.18.4-Linux-x86_64/share/cmake-3.18/Modules/FindPackageHandleStandardArgs.cmake:165 (message): Could NOT find Threads (missing: Threads_FOUND) Call Stack (most recent call first): /__t/cmake/3.18.4/x64/cmake-3.18.4-Linux-x86_64/share/cmake-3.18/Modules/FindPackageHandleStandardArgs.cmake:458 (_FPHSA_FAILURE_MESSAGE) /__t/cmake/3.18.4/x64/cmake-3.18.4-Linux-x86_64/share/cmake-3.18/Modules/FindThreads.cmake:234 (FIND_PACKAGE_HANDLE_STANDARD_ARGS) tests/test_embed/CMakeLists.txt:17 (find_package) ``` CI: libc6-dev from GCC for ICC CI: Run bare metal for oneAPI CI: Ubuntu 18.04 for oneAPI CI: Intel +Catch -Eigen CI: CMake from Apt (ICC tests) CI: Replace Intel Py with GCC Py CI: Intel w/o GCC's Eigen CI: ICC with verbose make [Debug] Find core dump tests: use arg{} instead of arg() for Intel tests: adding a few more missing {} fix: sync with @tobiasleibner's branch fix: try ubuntu 20-04 fix: drop exit 1 docs: Apply suggestions from code review Co-authored-by: Tobias Leibner <tobias.leibner@googlemail.com> Workaround for ICC enable_if issues Another workaround for ICC's enable_if issues fix error in previous commit Disable one test for the Intel compiler in C++17 mode Add back one instance of py::arg().noconvert() Add NOLINT to fix clang-tidy check Work around for ICC internal error in PYBIND11_EXPAND_SIDE_EFFECTS in C++17 mode CI: Intel ICC with C++17 docs: pybind11/numpy.h does not require numpy at build time. (#2720) This is nice enough to be mentioned explicitly in the docs. docs: Update warning about Python 3.9.0 UB, now that 3.9.1 has been released (#2719) Adjusting `type_caster<std::reference_wrapper<T>>` to support const/non-const propagation in `cast_op`. (#2705) * Allow type_caster of std::reference_wrapper<T> to be the same as a native reference. Before, both std::reference_wrapper<T> and std::reference_wrapper<const T> would invoke cast_op<type>. This doesn't allow the type_caster<> specialization for T to distinguish reference_wrapper types from value types. After, the type_caster<> specialization invokes cast_op<type&>, which allows reference_wrapper to behave in the same way as a native reference type. * Add tests/examples for std::reference_wrapper<const T> * Add tests which use mutable/immutable variants This test is a chimera; it blends the pybind11 casters with a custom pytype implementation that supports immutable and mutable calls. In order to detect the immutable/mutable state, the cast_op needs to propagate it, even through e.g. std::reference<const T> Note: This is still a work in progress; some things are crashing, which likely means that I have a refcounting bug or something else missing. * Add/finish tests that distinguish const& from & Fixes the bugs in my custom python type implementation, demonstrate test that requires const& and reference_wrapper<const T> being treated differently from Non-const. * Add passing a const to non-const method. * Demonstrate non-const conversion of reference_wrapper in tests. Apply formatting presubmit check. * Fix build errors from presubmit checks. * Try and fix a few more CI errors * More CI fixes. * More CI fixups. * Try and get PyPy to work. * Additional minor fixups. Getting close to CI green. * More ci fixes? * fix clang-tidy warnings from presubmit * fix more clang-tidy warnings * minor comment and consistency cleanups * PyDECREF -> Py_DECREF * copy/move constructors * Resolve codereview comments * more review comment fixes * review comments: remove spurious & * Make the test fail even when the static_assert is commented out. This expands the test_freezable_type_caster a bit by: 1/ adding accessors .is_immutable and .addr to compare identity from python. 2/ Changing the default cast_op of the type_caster<> specialization to return a non-const value. In normal codepaths this is a reasonable default. 3/ adding roundtrip variants to exercise the by reference, by pointer and by reference_wrapper in all call paths. In conjunction with 2/, this demonstrates the failure case of the existing std::reference_wrpper conversion, which now loses const in a similar way that happens when using the default cast_op_type<>. * apply presubmit formatting * Revert inclusion of test_freezable_type_caster There's some concern that this test is a bit unwieldly because of the use of the raw <Python.h> functions. Removing for now. * Add a test that validates const references propagation. This test verifies that cast_op may be used to correctly detect const reference types when used with std::reference_wrapper. * mend * Review comments based changes. 1. std::add_lvalue_reference<type> -> type& 2. Simplify the test a little more; we're never returning the ConstRefCaster type so the class_ definition can be removed. * formatted files again. * Move const_ref_caster test to builtin_casters * Review comments: use cast_op and adjust some comments. * Simplify ConstRefCasted test I like this version better as it moves the assertion that matters back into python. ci: drop pypy2 linux, PGI 20.7, add Python 10 dev (#2724) * ci: drop pypy2 linux, add Python 10 dev * ci: fix mistake * ci: commented-out PGI 20.11, drop 20.7 fix: regression with installed pybind11 overriding local one (#2716) * fix: regression with installed pybind11 overriding discovered one Closes #2709 * docs: wording incorrect style: remove redundant instance->owned = true (#2723) which was just before set to True in instance->allocate_layout() fix: also throw in the move-constructor added by the PYBIND11_OBJECT macro, after the argument has been moved-out (if necessary) (#2701) Make args_are_all_* ICC workarounds unconditional Disable test_aligned on Intel ICC Fix test_aligned on Intel ICC Skip test_python_alreadyset_in_destructor on Intel ICC Fix test_aligned again ICC CI: Downgrade pytest pytest 6 does not capture the `discard_as_unraisable` stderr and just writes a warning with its content instead. * refactor: simpler Intel workaround, suggested by @laramiel * fix: try version with impl to see if it is easier to compile * docs: update README for ICC Co-authored-by: Axel Huebl <axel.huebl@plasma.ninja> Co-authored-by: Henry Schreiner <henryschreineriii@gmail.com>
2021-01-18 00:53:07 +00:00
4. Intel classic C++ compiler 18 or newer (ICC 20.2 tested in CI)
5. Cygwin/GCC (previously tested on 2.5.1)
fix: Intel ICC C++17 compatibility (#2729) * CI: Intel icc/icpc via oneAPI Add testing for Intel icc/icpc via the oneAPI images. Intel oneAPI is in a late beta stage, currently shipping oneAPI beta09 with ICC 20.2. CI: Skip Interpreter Tests for Intel Cannot find how to add this, neiter the package `libc6-dev` nor `intel-oneapi-mkl-devel` help when installed to solve this: ``` -- Looking for C++ include pthread.h -- Looking for C++ include pthread.h - not found CMake Error at /__t/cmake/3.18.4/x64/cmake-3.18.4-Linux-x86_64/share/cmake-3.18/Modules/FindPackageHandleStandardArgs.cmake:165 (message): Could NOT find Threads (missing: Threads_FOUND) Call Stack (most recent call first): /__t/cmake/3.18.4/x64/cmake-3.18.4-Linux-x86_64/share/cmake-3.18/Modules/FindPackageHandleStandardArgs.cmake:458 (_FPHSA_FAILURE_MESSAGE) /__t/cmake/3.18.4/x64/cmake-3.18.4-Linux-x86_64/share/cmake-3.18/Modules/FindThreads.cmake:234 (FIND_PACKAGE_HANDLE_STANDARD_ARGS) tests/test_embed/CMakeLists.txt:17 (find_package) ``` CI: libc6-dev from GCC for ICC CI: Run bare metal for oneAPI CI: Ubuntu 18.04 for oneAPI CI: Intel +Catch -Eigen CI: CMake from Apt (ICC tests) CI: Replace Intel Py with GCC Py CI: Intel w/o GCC's Eigen CI: ICC with verbose make [Debug] Find core dump tests: use arg{} instead of arg() for Intel tests: adding a few more missing {} fix: sync with @tobiasleibner's branch fix: try ubuntu 20-04 fix: drop exit 1 docs: Apply suggestions from code review Co-authored-by: Tobias Leibner <tobias.leibner@googlemail.com> Workaround for ICC enable_if issues Another workaround for ICC's enable_if issues fix error in previous commit Disable one test for the Intel compiler in C++17 mode Add back one instance of py::arg().noconvert() Add NOLINT to fix clang-tidy check Work around for ICC internal error in PYBIND11_EXPAND_SIDE_EFFECTS in C++17 mode CI: Intel ICC with C++17 docs: pybind11/numpy.h does not require numpy at build time. (#2720) This is nice enough to be mentioned explicitly in the docs. docs: Update warning about Python 3.9.0 UB, now that 3.9.1 has been released (#2719) Adjusting `type_caster<std::reference_wrapper<T>>` to support const/non-const propagation in `cast_op`. (#2705) * Allow type_caster of std::reference_wrapper<T> to be the same as a native reference. Before, both std::reference_wrapper<T> and std::reference_wrapper<const T> would invoke cast_op<type>. This doesn't allow the type_caster<> specialization for T to distinguish reference_wrapper types from value types. After, the type_caster<> specialization invokes cast_op<type&>, which allows reference_wrapper to behave in the same way as a native reference type. * Add tests/examples for std::reference_wrapper<const T> * Add tests which use mutable/immutable variants This test is a chimera; it blends the pybind11 casters with a custom pytype implementation that supports immutable and mutable calls. In order to detect the immutable/mutable state, the cast_op needs to propagate it, even through e.g. std::reference<const T> Note: This is still a work in progress; some things are crashing, which likely means that I have a refcounting bug or something else missing. * Add/finish tests that distinguish const& from & Fixes the bugs in my custom python type implementation, demonstrate test that requires const& and reference_wrapper<const T> being treated differently from Non-const. * Add passing a const to non-const method. * Demonstrate non-const conversion of reference_wrapper in tests. Apply formatting presubmit check. * Fix build errors from presubmit checks. * Try and fix a few more CI errors * More CI fixes. * More CI fixups. * Try and get PyPy to work. * Additional minor fixups. Getting close to CI green. * More ci fixes? * fix clang-tidy warnings from presubmit * fix more clang-tidy warnings * minor comment and consistency cleanups * PyDECREF -> Py_DECREF * copy/move constructors * Resolve codereview comments * more review comment fixes * review comments: remove spurious & * Make the test fail even when the static_assert is commented out. This expands the test_freezable_type_caster a bit by: 1/ adding accessors .is_immutable and .addr to compare identity from python. 2/ Changing the default cast_op of the type_caster<> specialization to return a non-const value. In normal codepaths this is a reasonable default. 3/ adding roundtrip variants to exercise the by reference, by pointer and by reference_wrapper in all call paths. In conjunction with 2/, this demonstrates the failure case of the existing std::reference_wrpper conversion, which now loses const in a similar way that happens when using the default cast_op_type<>. * apply presubmit formatting * Revert inclusion of test_freezable_type_caster There's some concern that this test is a bit unwieldly because of the use of the raw <Python.h> functions. Removing for now. * Add a test that validates const references propagation. This test verifies that cast_op may be used to correctly detect const reference types when used with std::reference_wrapper. * mend * Review comments based changes. 1. std::add_lvalue_reference<type> -> type& 2. Simplify the test a little more; we're never returning the ConstRefCaster type so the class_ definition can be removed. * formatted files again. * Move const_ref_caster test to builtin_casters * Review comments: use cast_op and adjust some comments. * Simplify ConstRefCasted test I like this version better as it moves the assertion that matters back into python. ci: drop pypy2 linux, PGI 20.7, add Python 10 dev (#2724) * ci: drop pypy2 linux, add Python 10 dev * ci: fix mistake * ci: commented-out PGI 20.11, drop 20.7 fix: regression with installed pybind11 overriding local one (#2716) * fix: regression with installed pybind11 overriding discovered one Closes #2709 * docs: wording incorrect style: remove redundant instance->owned = true (#2723) which was just before set to True in instance->allocate_layout() fix: also throw in the move-constructor added by the PYBIND11_OBJECT macro, after the argument has been moved-out (if necessary) (#2701) Make args_are_all_* ICC workarounds unconditional Disable test_aligned on Intel ICC Fix test_aligned on Intel ICC Skip test_python_alreadyset_in_destructor on Intel ICC Fix test_aligned again ICC CI: Downgrade pytest pytest 6 does not capture the `discard_as_unraisable` stderr and just writes a warning with its content instead. * refactor: simpler Intel workaround, suggested by @laramiel * fix: try version with impl to see if it is easier to compile * docs: update README for ICC Co-authored-by: Axel Huebl <axel.huebl@plasma.ninja> Co-authored-by: Henry Schreiner <henryschreineriii@gmail.com>
2021-01-18 00:53:07 +00:00
6. NVCC (CUDA 11.0 tested in CI)
7. NVIDIA PGI (20.9 tested in CI)
About
-----
This project was created by `Wenzel
Jakob <http://rgl.epfl.ch/people/wjakob>`_. Significant features and/or
improvements to the code were contributed by Jonas Adler, Lori A. Burns,
Sylvain Corlay, Eric Cousineau, Aaron Gokaslan, Ralf Grosse-Kunstleve, Trent Houliston, Axel
2020-10-20 14:56:02 +00:00
Huebl, @hulucc, Yannick Jadoul, Sergey Lyskov Johan Mabille, Tomasz Miąsko,
Dean Moldovan, Ben Pritchard, Jason Rhinelander, Boris Schäling, Pim
2020-10-20 14:56:02 +00:00
Schellart, Henry Schreiner, Ivan Smirnov, Boris Staletic, and Patrick Stewart.
2020-10-20 19:14:40 +00:00
We thank Google for a generous financial contribution to the continuous
integration infrastructure used by this project.
Contributing
~~~~~~~~~~~~
See the `contributing
guide <https://github.com/pybind/pybind11/blob/master/.github/CONTRIBUTING.md>`_
for information on building and contributing to pybind11.
License
~~~~~~~
pybind11 is provided under a BSD-style license that can be found in the
`LICENSE <https://github.com/pybind/pybind11/blob/master/LICENSE>`_
file. By using, distributing, or contributing to this project, you agree
to the terms and conditions of this license.
2020-09-17 21:53:35 +00:00
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