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| # pybind11 — Seamless operability between C++11 and Python |
| |
| [](http://pybind11.readthedocs.org/en/master/?badge=master) |
| [](http://pybind11.readthedocs.org/en/stable/?badge=stable) |
| [](https://gitter.im/pybind/Lobby) |
| [](https://travis-ci.org/pybind/pybind11) |
| [](https://ci.appveyor.com/project/wjakob/pybind11) |
| |
| **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 isn't relevant for binding generation. Without |
| comments, the core header files only require ~4K lines of code and depend on |
| Python (2.7 or 3.x, or PyPy2.7 >= 5.7) 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 |
| [http://pybind11.readthedocs.org/en/master](http://pybind11.readthedocs.org/en/master). |
| A PDF version of the manual is available |
| [here](https://media.readthedocs.org/pdf/pybind11/master/pybind11.pdf). |
| |
| ## 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 |
| - Iterators and ranges |
| - 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.x, and PyPy (PyPy2.7 >= 5.7) 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. |
| |
| - It's 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**. |
| |
| - When supported by the compiler, two new C++14 features (relaxed constexpr and |
| return value deduction) are used to precompute function signatures at compile |
| time, 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 Xcode's clang, this is 5.0.0 or newer) |
| 2. GCC 4.8 or newer |
| 3. Microsoft Visual Studio 2015 Update 3 or newer |
| 4. Intel C++ compiler 16 or newer (15 with a [workaround](https://github.com/pybind/pybind11/issues/276)) |
| 5. Cygwin/GCC (tested on 2.5.1) |
| |
| ## 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, |
| Sylvain Corlay, |
| Trent Houliston, |
| Axel Huebl, |
| @hulucc, |
| Sergey Lyskov |
| Johan Mabille, |
| Tomasz Miąsko, |
| Dean Moldovan, |
| Ben Pritchard, |
| Jason Rhinelander, |
| Boris Schäling, |
| Pim Schellart, |
| Ivan Smirnov, and |
| Patrick Stewart. |
| |
| ### License |
| |
| pybind11 is provided under a BSD-style license that can be found in the |
| ``LICENSE`` file. By using, distributing, or contributing to this project, |
| you agree to the terms and conditions of this license. |
