use boost.python to Warp C++ for python

在python中调用c++

c++ 速度快，python 比较方便，如果同时用到python和c++中库，则需要相互调用。目前python发展迅速，很多新库都以python为主，但一些传统或者强调速度的库依然是用c++写的。因此掌握这一技能，可以加速开发，避免重复地制造车轮。

介绍

在python中调用c++的方法很多，出名的有swig, boost.python，个人属于刚入门，由于对boost库有好感，觉得代表着c++方面最先进的技术。boost.python的理念也很好，不用去学习接口语言，不用修改源代码，直接快速上手。

官方文档

• quick start
• 接口语法
• bjam documence

写一个小测试

• cpp.cpp: c++源文件
• py.py: python 测试文件
• Jamroot: boost.python 配置文件

安装boost环境

sudo apt-get install libboost-all-dev

再下载一个boost 源代码，这样可以进行下面的官方测试并得到配置文件Jamroot

官方测试

• hello world
• cd /home/yzbx/Downloads/boost_1_61_0/libs/python/example/tutorial
• bjam

warning: mismatched versions of Boost.Build engine and corewarning: Boost.Build engine (bjam) is 2014.03.00warning: Boost.Build core (at /media/yzbx/NewPartition/home/yzbx/Downloads/boost_1_61_0/tools/build/src) is 2015.07-gitnotice: no Python configured in user-config.jamnotice: will use default configurationwarning: No toolsets are configured.warning: Configuring default toolset "gcc".warning: If the default is wrong, your build may not work correctly.warning: Use the "toolset=xxxxx" option to override our guess.warning: For more configuration options, please consultwarning: http://boost.org/boost-build2/doc/html/bbv2/advanced/configuration.htmlPerforming configuration checks    - 32-bit                   : no  (cached)    - 64-bit                   : yes (cached)    - arm                      : no  (cached)    - mips1                    : no  (cached)    - power                    : no  (cached)    - sparc                    : no  (cached)    - x86                      : yes (cached)    - symlinks supported       : yes (cached)...patience......patience......found 1833 targets...

• python hello.py

hello, world

• 官方测试目录，输出一大堆如bin,xxx.so

$: tree /home/yzbx/Downloads/boost_1_61_0/libs/python/example/tutorial/home/yzbx/Downloads/boost_1_61_0/libs/python/example/tutorial├── bin│   ├── config.log│   ├── gcc-5.4.0│   │   └── debug│   │       ├── hello_ext.so│   │       └── hello.o│   ├── hello.test│   │   └── gcc-5.4.0│   │       └── debug│   │           ├── hello│   │           ├── hello.output│   │           └── hello.test│   └── project-cache.jam├── hello.cpp├── hello_ext.so├── hello.py├── Jamroot├── libboost_python.so -> libboost_python.so.1.61.0├── libboost_python.so.1 -> libboost_python.so.1.61.0├── libboost_python.so.1.61 -> libboost_python.so.1.61.0└── libboost_python.so.1.61.0

• 上面的命令运行成功，说明安装boost.python环境成功！

在ubuntu16.04上基于官方测试进行更改

1. struct or class ? 写c++一般用class，不过用class就要加public，否则默认为private就无法在python中调用。
2. bjam 如何使用配置？

Simply copy the file and tweak use-project boost to where your boost root directory is and you're OK.The comments contained in the Jamrules file above should be sufficient to get you going. 

上面说只要指定boost的根目录，再按Jamroot中的注释去更改就okay!

3. 如上图，在个人测试文件夹下有三个文件：cpp.cpp,py.py,Jamroot，将root根目录设置为/home/yzbx/Downloads/boost_1_61_0, 再将python 模块名改为yzbx_ext，再将源文件和测试文件改为cpp.cpp,py.py, 并将测试输出目录改为yzbx
4. 个人测试文件的输出，通过对比，不难了解各个参数的含义

$: tree ~/test/boost-python//home/yzbx/test/boost-python/├── bin│   ├── config.log│   ├── gcc-5.4.0│   │   └── debug│   │       ├── cpp.o│   │       └── yzbx_ext.so│   ├── project-cache.jam│   └── yzbx.test│       └── gcc-5.4.0│           └── debug│               ├── yzbx│               ├── yzbx.output│               └── yzbx.test├── cpp.cpp├── Jamroot├── libboost_python.so -> libboost_python.so.1.61.0├── libboost_python.so.1 -> libboost_python.so.1.61.0├── libboost_python.so.1.61 -> libboost_python.so.1.61.0├── libboost_python.so.1.61.0├── py.py└── yzbx_ext.so

附件

cpp.cpp

//  Copyright Joel de Guzman 2002-2004. Distributed under the Boost//  Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt//  or copy at http://www.boost.org/LICENSE_1_0.txt)//  Hello World Example from the tutorial//  [Joel de Guzman 10/9/2002]#include <boost/python.hpp>#include <boost/python/module.hpp>#include <boost/python/def.hpp>char const* greet(){   return "hello, world";}int add(int a,int b){    return a+b;}struct bgs{void set(int a){this->a=a;}int getA(){return a;}    int a;};class Var{public:    Var(std::string name) : name(name), value() {}    std::string const name;    float value;};BOOST_PYTHON_MODULE(yzbx_ext){    using namespace boost::python;    def("greet", greet);    def("add",add);    class_<bgs>("bgs")        .def("set",&bgs::set)        .def("getA",&bgs::getA)        .def_readonly("a",&bgs::a)    ;    class_<Var>("Var", init<std::string>())    .def_readonly("name", &Var::name)    .def_readwrite("value", &Var::value);}

py.py

#  Copyright Joel de Guzman 2002-2007. Distributed under the Boost#  Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt#  or copy at http://www.boost.org/LICENSE_1_0.txt)#  Hello World Example from the tutorialimport yzbx_extprint yzbx_ext.greet()print yzbx_ext.add(3,5)bgs=yzbx_ext.bgs()bgs.set(10)print bgs.getA()var=yzbx_ext.Var("pi")var.value=3.14print var.name,' is around ', var.value

Jamroot

# Copyright David Abrahams 2006. Distributed under the Boost# Software License, Version 1.0. (See accompanying# file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)import python ;if ! [ python.configured ]{    ECHO "notice: no Python configured in user-config.jam" ;    ECHO "notice: will use default configuration" ;    using python ;}# Specify the path to the Boost project.  If you move this project,# adjust this path to refer to the Boost root directory.use-project boost  : /home/yzbx/Downloads/boost_1_61_0 ;# Set up the project-wide requirements that everything uses the# boost_python library from the project whose global ID is# /boost/python.project  : requirements <library>/boost/python//boost_python                  <implicit-dependency>/boost//headers   : usage-requirements <implicit-dependency>/boost//headers   ;# Declare the three extension modules.  You can specify multiple# source files after the colon separated by spaces.python-extension yzbx_ext : cpp.cpp ;# Put the extension and Boost.Python DLL in the current directory, so# that running script by hand works.install convenient_copy   : yzbx_ext   : <install-dependencies>on <install-type>SHARED_LIB <install-type>PYTHON_EXTENSION     <location>.   ;# A little "rule" (function) to clean up the syntax of declaring tests# of these extension modules.local rule run-test ( test-name : sources + ){    import testing ;    testing.make-test run-pyd : $(sources) : : $(test-name) ;}# Declare test targetsrun-test yzbx : yzbx_ext py.py ;