ctypes 初步使用

对C++不熟，在python中调用c++程序

无参数函数直接调用

先撰写.cpp程序

#include <iostream>

extern "C"
{

void bbar(){
std::cout<<"Hello"<<std::endl;
}
}       

编译.cpp为.so文件(每次写完cpp都得编译一次)

g++ -std=c++11 -shared -fPIC -o t.so t.cpp -I/usr/include/python3.6

.py 程序

#!/usr/bin/env python
# coding=utf-8

from ctypes import cdll
lib = cdll.LoadLibrary('t.so')


if __name__=="__main__":
    lib.bbar()   

有参数函数调用

cpp

#include <iostream>

extern "C"
{

int bbar(int a, int b){
return a+b;
}
}

 py

#!/usr/bin/env python
# coding=utf-8

from ctypes import cdll
lib = cdll.LoadLibrary('t.so')


if __name__=="__main__":
    #f = F()
    a = lib.bbar(1,2)
    print(a)

类的调用 

感觉ctypes调用class 不是很方便啊，查到一些demo，class实例化还是在c++里

.cpp文件

#include <iostream>
#include <ostream>
#include <type_traits>
#include <typeinfo>


using namespace std;


class Test
{

public:
    int add(int a, int b);
    int subtraction(int a, int b);
    void print(const char *s);
    
};

int Test::add(int a, int b)
{
    return a+b;
}

int Test::subtraction(int a, int b){
    return a-b;
}

void Test::print(const char *s){
cout << s <<endl;
};


extern "C"{
    Test T;
    int _add(int a, int b){
        int c;
        c = T.add(a,b);
        return c;
    }
    int _sub(int a, int b){
        int c;
        c = T.subtraction(a,b);
        return c;
    }
    void _print(const char *s){
        T.print("c++");
        //if (typeid(s).name() == "string")
        T.print(s);
    }
}

编译成动态库后

.py文件

#!/usr/bin/env python
# coding=utf-8

from ctypes import cdll,c_char_p
lib = cdll.LoadLibrary('t.so')


if __name__=="__main__":
    # f = lib.T()

    a = lib._add(1,2)
    b = lib._sub(1,2)
    print(a)
    print(b)
    lib._print(c_char_p(bytes("python", 'utf-8')))

要通过 c_char_p 把输入转成char 指针，否则只会print 第一个字符"p".