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144 lines
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144 lines
6.1 KiB
Markdown
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# pybind11 — Seamless operability between C++11 and Python
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[](http://pybind11.readthedocs.org/en/master/?badge=master)
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[](http://pybind11.readthedocs.org/en/stable/?badge=stable)
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[](https://gitter.im/pybind/Lobby)
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[](https://github.com/pybind/pybind11/actions)
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[](https://ci.appveyor.com/project/wjakob/pybind11)
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**pybind11** is a lightweight header-only library that exposes C++ types in
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Python and vice versa, mainly to create Python bindings of existing C++ code.
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Its goals and syntax are similar to the excellent [Boost.Python][] library by
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David Abrahams: to minimize boilerplate code in traditional extension modules
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by inferring type information using compile-time introspection.
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The main issue with Boost.Python—and the reason for creating such a similar
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project—is Boost. Boost is an enormously large and complex suite of utility
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libraries that works with almost every C++ compiler in existence. This
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compatibility has its cost: arcane template tricks and workarounds are
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necessary to support the oldest and buggiest of compiler specimens. Now that
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C++11-compatible compilers are widely available, this heavy machinery has
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become an excessively large and unnecessary dependency.
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Think of this library as a tiny self-contained version of Boost.Python with
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everything stripped away that isn't relevant for binding generation. Without
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comments, the core header files only require ~4K lines of code and depend on
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Python (2.7 or 3.5+, or PyPy) and the C++ standard library. This compact
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implementation was possible thanks to some of the new C++11 language features
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(specifically: tuples, lambda functions and variadic templates). Since its
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creation, this library has grown beyond Boost.Python in many ways, leading to
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dramatically simpler binding code in many common situations.
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Tutorial and reference documentation is provided at
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[pybind11.readthedocs.org][]. A PDF version of the manual is available
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[here][docs-pdf].
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## Core features
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pybind11 can map the following core C++ features to Python:
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- Functions accepting and returning custom data structures per value, reference, or pointer
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- Instance methods and static methods
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- Overloaded functions
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- Instance attributes and static attributes
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- Arbitrary exception types
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- Enumerations
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- Callbacks
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- Iterators and ranges
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- Custom operators
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- Single and multiple inheritance
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- STL data structures
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- Smart pointers with reference counting like `std::shared_ptr`
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- Internal references with correct reference counting
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- C++ classes with virtual (and pure virtual) methods can be extended in Python
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## Goodies
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In addition to the core functionality, pybind11 provides some extra goodies:
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- Python 2.7, 3.5+, and PyPy (tested on 7.3) are supported with an implementation-agnostic
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interface.
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- It is possible to bind C++11 lambda functions with captured variables. The
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lambda capture data is stored inside the resulting Python function object.
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- pybind11 uses C++11 move constructors and move assignment operators whenever
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possible to efficiently transfer custom data types.
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- It's easy to expose the internal storage of custom data types through
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Pythons' buffer protocols. This is handy e.g. for fast conversion between
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C++ matrix classes like Eigen and NumPy without expensive copy operations.
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- pybind11 can automatically vectorize functions so that they are transparently
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applied to all entries of one or more NumPy array arguments.
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- Python's slice-based access and assignment operations can be supported with
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just a few lines of code.
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- Everything is contained in just a few header files; there is no need to link
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against any additional libraries.
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- Binaries are generally smaller by a factor of at least 2 compared to
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equivalent bindings generated by Boost.Python. A recent pybind11 conversion
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of PyRosetta, an enormous Boost.Python binding project,
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[reported][pyrosetta-report] a binary size reduction of **5.4x** and compile
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time reduction by **5.8x**.
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- Function signatures are precomputed at compile time (using `constexpr`),
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leading to smaller binaries.
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- With little extra effort, C++ types can be pickled and unpickled similar to
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regular Python objects.
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## Supported compilers
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1. Clang/LLVM 3.3 or newer (for Apple Xcode's clang, this is 5.0.0 or newer)
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2. GCC 4.8 or newer
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3. Microsoft Visual Studio 2015 Update 3 or newer
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4. Intel C++ compiler 17 or newer (16 with pybind11 v2.0 and 15 with pybind11
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v2.0 and a [workaround][intel-15-workaround])
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5. Cygwin/GCC (tested on 2.5.1)
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## About
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This project was created by [Wenzel Jakob](http://rgl.epfl.ch/people/wjakob).
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Significant features and/or improvements to the code were contributed by
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Jonas Adler,
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Lori A. Burns,
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Sylvain Corlay,
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Trent Houliston,
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Axel Huebl,
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@hulucc,
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Sergey Lyskov
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Johan Mabille,
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Tomasz Miąsko,
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Dean Moldovan,
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Ben Pritchard,
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Jason Rhinelander,
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Boris Schäling,
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Pim Schellart,
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Henry Schreiner,
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Ivan Smirnov, and
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Patrick Stewart.
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### Contributing
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See the [contributing guide][] for information on building and contributing to
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pybind11.
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### License
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pybind11 is provided under a BSD-style license that can be found in the
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[`LICENSE`][] file. By using, distributing, or contributing to this project,
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you agree to the terms and conditions of this license.
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[pybind11.readthedocs.org]: http://pybind11.readthedocs.org/en/master
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[docs-pdf]: https://media.readthedocs.org/pdf/pybind11/master/pybind11.pdf
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[Boost.Python]: http://www.boost.org/doc/libs/1_58_0/libs/python/doc/
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[pyrosetta-report]: http://graylab.jhu.edu/RosettaCon2016/PyRosetta-4.pdf
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[contributing guide]: https://github.com/pybind/pybind11/blob/master/.github/CONTRIBUTING.md
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[`LICENSE`]: https://github.com/pybind/pybind11/blob/master/LICENSE
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[intel-15-workaround]: https://github.com/pybind/pybind11/issues/276
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