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

曾经终败给现在 2022-02-13 01:19 310阅读 0赞

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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