Interfacing C++ and Python with pybind11 on windows 10

Series

Guide

requirements:

pybind11 v2.3.dev0

python 2.7

install pytest

pip install pytest

compile

git clone https://github.com/pybind/pybind11.git

cd pybind11

mkdir build

cd build

cmake-gui ..

with options

PYBIND11_CPP_STANDARD /std:c++11 # default c++14

PYTHON_EXECUTABLE C:/Python27/python.exe

CMAKE_INSTALL_PREFIX C:/Program Files/pybind11

compile with VS 2015 with x64 Release

install to C:\Program Files\pybind11 with only include and share

$ tree .

.

├── include

│   └── pybind11

│   ├── attr.h

│   ├── buffer_info.h

│   ├── cast.h

│   ├── chrono.h

│   ├── common.h

│   ├── complex.h

│   ├── detail

│   │   ├── class.h

│   │   ├── common.h

│   │   ├── descr.h

│   │   ├── init.h

│   │   ├── internals.h

│   │   └── typeid.h

│   ├── eigen.h

│   ├── embed.h

│   ├── eval.h

│   ├── functional.h

│   ├── iostream.h

│   ├── numpy.h

│   ├── operators.h

│   ├── options.h

│   ├── pybind11.h

│   ├── pytypes.h

│   ├── stl.h

│   └── stl_bind.h

└── share

└── cmake

└── pybind11

├── FindPythonLibsNew.cmake

├── pybind11Config.cmake

├── pybind11ConfigVersion.cmake

├── pybind11Targets.cmake

└── pybind11Tools.cmake

6 directories, 29 files

Usage

pybind11 (cpp--->python)

module: examplelib

target: examplelib

cpp: example.cpp

example.cpp

#include

namespace py = pybind11;

int add(int i, int j) {

return i + j;

}

/*

#include

namespace py = pybind11;

int add(int i, int j) {

return i + j;

}

struct Pet {

Pet(const std::string &name) : name(name) { }

void setName(const std::string &name_) { name = name_; }

const std::string &getName() const { return name; }

std::string name;

};

/*

module: examplelib

target: examplelib

cpp: example.cpp

*/

PYBIND11_MODULE(examplelib, m)

{

// optional module docstring

m.doc() = "pybind11 example plugin";

// FUNCTIONS

// expose add function, and add keyword arguments and default arguments

m.def("add", &add, "A function which adds two numbers", py::arg("i") = 1, py::arg("j") = 2);

// DATA

// exporting variables

m.attr("the_answer") = 42;

py::object world = py::cast("World");

m.attr("what") = world;

// CLASSES

py::class_(m, "Pet")

.def(py::init())

.def("setName", &Pet::setName)

.def("getName", &Pet::getName);

/*

python3

> help(examplelib)

*/

}

CMakeLists.txt

cmake_minimum_required (VERSION 2.6)

project (pybind)

enable_language(C)

enable_language(CXX)

find_package(pybind11 CONFIG REQUIRED)

include_directories(${pybind11_INCLUDE_DIRS})

message([MAIN] "Found pybind11 v${pybind11_VERSION}: ${pybind11_INCLUDE_DIRS}")

MESSAGE( [Main] " pybind11_INCLUDE_DIRS = ${pybind11_INCLUDE_DIRS}")

MESSAGE( [Main] " pybind11_LIBRARIES = ${pybind11_LIBRARIES}")

#

# # Create an extension module

# add_library(mylib MODULE main.cpp)

# target_link_libraries(mylib pybind11::module)

#

# # Or embed the Python interpreter into an executable

# add_executable(myexe main.cpp)

# target_link_libraries(myexe pybind11::embed)

# method (1): generate `examplelib.pyd`

pybind11_add_module(examplelib example.cpp)

# method (2): generate `examplelib.dll` rename to `examplelib.pyd`

#add_library(examplelib MODULE example.cpp)

#target_link_libraries(examplelib pybind11::module)

MESSAGE( [Main] " pybind11_INCLUDE_DIRS = ${pybind11_INCLUDE_DIRS}")

MESSAGE( [Main] " pybind11_LIBRARIES = ${pybind11_LIBRARIES}")

#add_executable(cpp_use_python cpp_use_python.cpp)

#target_link_libraries(cpp_use_python PRIVATE pybind11::embed)

cmake and config

build with vs and we get 3 files:

examplelib.lib

examplelib.exp

examplelib.cp35-win_amd64.pyd

python import examplelib

python3

Python 3.5.3 (v3.5.3:1880cb95a742, Jan 16 2017, 16:02:32) [MSC v.1900 64 bit (AMD64)] on win32

Type "help", "copyright", "credits" or "license" for more information.

>>> import examplelib

>>> help(examplelib)

Help on module examplelib:

NAME

examplelib - pybind11 example plugin

CLASSES

pybind11_builtins.pybind11_object(builtins.object)

Pet

class Pet(pybind11_builtins.pybind11_object)

| Method resolution order:

| Pet

| pybind11_builtins.pybind11_object

| builtins.object

|

| Methods defined here:

|

| __init__(...)

| __init__(self: examplelib.Pet, arg0: str) -> None

|

| getName(...)

| getName(self: examplelib.Pet) -> str

|

| setName(...)

| setName(self: examplelib.Pet, arg0: str) -> None

|

| ----------------------------------------------------------------------

| Methods inherited from pybind11_builtins.pybind11_object:

|

| __new__(*args, **kwargs) from pybind11_builtins.pybind11_type

| Create and return a new object. See help(type) for accurate signature.

FUNCTIONS

add(...) method of builtins.PyCapsule instance

add(i: int = 1, j: int = 2) -> int

A function which adds two numbers

DATA

the_answer = 42

what = 'World'

FILE

e:\git\car\extra\pybind11\build\release\examplelib.cp35-win_amd64.pyd

>>> p = examplelib.Pet('kzl')

>>> print(p)

>>> p.getName()

'kzl'

>>> examplelib.add(1,2)

3

>>> examplelib.the_answer

42

>>> examplelib.what

'World'

>>>

embed

example.py

def add(i, j):

print("hello, pybind11")

return i+j

class MyMath:

def __init__(self,name):

self.name = name

def my_add(self,i,j):

return i + j

def my_strcon(self,a,b):

return a + b

cpp_use_python.cpp

#include

#include

namespace py = pybind11;

int main() {

py::scoped_interpreter python;

/*

import sys

print sys.path

print "Hello,World!"

*/

py::module sys = py::module::import("sys");

py::print(sys.attr("path"));

py::print("Hello, World!"); // use the Python API

/*

import example

n = example.add(1,2)

*/

py::module example = py::module::import("example");

py::object result = example.attr("add")(1, 2);

int n = result.cast();

assert(n == 3);

std::cout << "result from example.add(1,2) = " << n << std::endl;

/*

from example import MyMath

obj = MyMath("v0")

obj.my_add(1,2)

*/

py::object MyMath = py::module::import("example").attr("MyMath"); // class

py::object obj = MyMath("v0"); // class object

py::object my_add = obj.attr("my_add");// object method

py::object result2 = my_add(1, 2); // result

int n2 = result2.cast(); // cast from python type to c++ type

assert(n2 == 3);

std::cout << "result from obj.my_add(1,2) = " << n2 << std::endl;

/*

from example import MyMath

obj = MyMath("v0")

obj.my_strcon("abc","123");

*/

py::object my_strcon = obj.attr("my_strcon"); // object method

py::object result3 = my_strcon("abc", "123");

std::string str3 = result3.cast<:string>();

std::cout << "result from obj.my_strcon(abc,123) = " << str3 << std::endl;

return 0;

}

CMakeLists.txt

cmake_minimum_required (VERSION 2.6)

project (pybind)

enable_language(C)

enable_language(CXX)

find_package(pybind11 CONFIG REQUIRED)

include_directories(${pybind11_INCLUDE_DIRS})

MESSAGE( [Main] " pybind11_INCLUDE_DIRS = ${pybind11_INCLUDE_DIRS}")

MESSAGE( [Main] " pybind11_LIBRARIES = ${pybind11_LIBRARIES}")

add_executable(cpp_use_python cpp_use_python.cpp)

target_link_libraries(cpp_use_python PRIVATE pybind11::embed)

Reference

History

20180301: created.

Copyright

Post author: kezunlin

Copyright Notice: All articles in this blog are licensed under CC BY-NC-SA 3.0 unless stating additionally.