Python的C/C++扩展——boost_python编写Python模块

前面讲述了Python使用ctypes直接调用动态库和使用Python的C语言API封装C函数，本文概述方便封装C++类给Python使用的boost_python库。

安装boost python库：

sudo aptitude install libboost-python-dev 

示例

下面代码简单实现了一个普通函数maxab()和一个Student类：

#include <iostream> #include <string> int maxab(int a, int b) { return a>b?a:b; } class Student { private: int age; std::string name; public: Student() {} Student(std::string const& _name, int _age) { name=_name; age=_age; } static void myrole() { std::cout << "I'm a student!" << std::endl; } void whoami() { std::cout << "I am " << name << std::endl; } bool operator==(Student const& s) const { return age == s.age; } bool operator!=(Student const& s) const { return age != s.age; } }; 

使用boost.python库封装也很简单，如下代码所示：

#include <Python.h> #include <boost/python.hpp> #include <boost/python/suite/indexing/vector_indexing_suite.hpp> #include <vector> #include "student.h" using namespace boost::python; BOOST_PYTHON_MODULE(student) { // This will enable user-defined docstrings and python signatures, // while disabling the C++ signatures scope().attr("__version__") = "1.0.0"; scope().attr("__doc__") = "a demo module to use boost_python."; docstring_options local_docstring_options(true, false, false); def( "maxab", &maxab, "return max of two numbers.\n" ); class_<Student>("Student", "a class of student") .def(init<>()) .def(init<std::string, int>()) // methods for Chinese word segmentation .def( "whoami", &Student::whoami, "method's doc string..." ) .def( "myrole", &Student::myrole, "method's doc string..." ) .staticmethod("myrole"); // 封装STL class_<std::vector<Student> >("StudentVec") .def(vector_indexing_suite<std::vector<Student> >()) ; } 

上述代码还是include了Python.h文件，如果不include的话，会报错误：

wrap_python.hpp:50:23: fatal error: pyconfig.h: No such file or directory 

编译

编译以上代码有两种方式，一种是在命令行下面直接使用g++编译：

g++ -I/usr/include/python2.7 -fPIC wrap_student.cpp -lboost_python -shared -o student.so 

首先指定Python.h的路径，如果是Python 3的话就要修改为相应的路径，编译wrap_student.cpp要指定-fPIC参数，链接(-lboost_python)生成动态库(-shared)。 生成的student.so动态库就可以被python直接import使用了

In [1]: import student

In [2]: student.maxab(2, 5)
Out[2]: 5

In [3]: s = student.Student('Tom', 12)

In [4]: s.whoami()
I am Tom

In [5]: s.myrole()
I'm a student!
另外一直方法是用python的setuptools编写setup.py脚本：

#!/usr/bin/env python from setuptools import setup, Extension setup(name="student", ext_modules=[ Extension("student", ["wrap_student.cpp"], libraries = ["boost_python"]) ]) 

然后执行命令编译：

python setup.py build or sudo python setup.py install 

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