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| .. image:: pybind11-logo.png | |
| About this project | |
| ================== | |
| **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`_ library by David | |
| Abrahams: to minimize boilerplate code in traditional extension modules by | |
| inferring type information using compile-time introspection. | |
| .. _Boost.Python: http://www.boost.org/doc/libs/release/libs/python/doc/index.html | |
| 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. | |
| Core features | |
| ************* | |
| The following core C++ features can be mapped 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.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 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. | |
| .. _PyRosetta: http://graylab.jhu.edu/RosettaCon2016/PyRosetta-4.pdf | |
| Supported compilers | |
| ******************* | |
| 1. Clang/LLVM (any non-ancient version with C++11 support) | |
| 2. GCC 4.8 or newer | |
| 3. Microsoft Visual Studio 2015 or newer | |
| 4. Intel C++ compiler v17 or newer (v16 with pybind11 v2.0 and v15 with pybind11 v2.0 and a `workaround <https://github.com/pybind/pybind11/issues/276>`_ ) | |