Python調用C/C++的種種方法

Python調用C/C++的種種方法 

2010-12-07 09:59 28433人閱讀 評論(1) 收藏

Python是解釋性語言, 底層就是用c實現的, 因此用python調用C是很容易的, 下面就總結一下各類調用的方法, 給出例子, 全部例子都在ubuntu9.10, python2.6下試過.

 

 

 

1. Python 調用 C (base)

 

想在python中調用c函數, 如這兒的fact

 

#include <Python.h>

 

int fact(int n)

{

  if (n <= 1)

    return 1;

  else

    return n * fact(n - 1);

}

 

PyObject* wrap_fact(PyObject* self, PyObject* args)

{

  int n, result;

 

  if (! PyArg_ParseTuple(args, "i:fact", &n))

    return NULL;

  result = fact(n);

  return Py_BuildValue("i", result);

}

 

static PyMethodDef exampleMethods[] =

{

  {"fact", wrap_fact, METH_VARARGS, "Caculate N!"},

  {NULL, NULL}

};

 

void initexample()

{

  PyObject* m;

  m = Py_InitModule("example", exampleMethods);

}

 

 

 

把這段代碼存爲wrapper.c, 編成so庫,

 

gcc -fPIC wrapper.c -o example.so -shared  -I/usr/include/python2.6 -I/usr/lib/python2.6/config

 

 

 

而後在有此so庫的目錄, 進入python, 能夠以下使用

 

import example

 

example.fact(4)

 

 

 

2. Python 調用 C++ (base)

 

在python中調用C++類成員函數, 以下調用TestFact類中的fact函數,

 

#include <Python.h>

 

class TestFact{

    public:

    TestFact(){};

    ~TestFact(){};

    int fact(int n);

};

 

int TestFact::fact(int n)

{

  if (n <= 1)

    return 1;

  else

    return n * (n - 1);

}

 

int fact(int n)

{

    TestFact t;

    return t.fact(n);

}

 

PyObject* wrap_fact(PyObject* self, PyObject* args)

{

  int n, result;

 

  if (! PyArg_ParseTuple(args, "i:fact", &n))

    return NULL;

  result = fact(n);

  return Py_BuildValue("i", result);

}

 

static PyMethodDef exampleMethods[] =

{

  {"fact", wrap_fact, METH_VARARGS, "Caculate N!"},

  {NULL, NULL}

};

 

extern "C"              //不加會致使找不到initexample

void initexample()

{

  PyObject* m;

  m = Py_InitModule("example", exampleMethods);

}

 

 

 

把這段代碼存爲wrapper.cpp, 編成so庫,

 

g++ -fPIC wrapper.cpp -o example.so -shared -I/usr/include/python2.6 -I/usr/lib/python2.6/config

 

 

 

而後在有此so庫的目錄, 進入python, 能夠以下使用

 

import example

 

example.fact(4)

 

 

 

3. Python 調用 C++ (Boost.Python)

 

Boost庫是很是強大的庫, 其中的python庫能夠用來封裝c++被python調用, 功能比較強大, 不但能夠封裝函數還能封裝類, 類成員.

 

http://dev.gameres.com/Program/Abstract/Building%20Hybrid%20Systems%20with%20Boost_Python.CHN.by.JERRY.htm

 

首先在ubuntu下安裝boost.python, apt-get install libboost-python-dev

 

#include <boost/python.hpp>

char const* greet()

{

   return "hello, world";

}

 

BOOST_PYTHON_MODULE(hello)

{

    using namespace boost::python;

    def("greet", greet);

}

 

把代碼存爲hello.cpp, 編譯成so庫

 

g++ hello.cpp -o hello.so -shared -I/usr/include/python2.5 -I/usr/lib/python2.5/config -lboost_python-gcc42-mt-1_34_1

 

 

 

此處python路徑設爲你的python路徑, 而且必須加-lboost_python-gcc42-mt-1_34_1, 這個庫名不必定是這個, 去/user/lib查

 

 

 

而後在有此so庫的目錄, 進入python, 能夠以下使用

 

>>> import hello

>>> hello.greet()

'hello, world'

 

 

 

4. python 調用 c++ (ctypes)

 

ctypes is an advanced ffi (Foreign Function Interface) package for Python 2.3 and higher. In Python 2.5 it is already included.

 

ctypes allows to call functions in dlls/shared libraries and has extensive facilities to create, access and manipulate simple and complicated C data types in Python - in other words: wrap libraries in pure Python. It is even possible to implement C callback functions in pure Python.

 

http://python.net/crew/theller/ctypes/

 

 

 

#include <Python.h>

 

class TestFact{

    public:

    TestFact(){};

    ~TestFact(){};

    int fact(int n);

};

 

int TestFact::fact(int n)

{

  if (n <= 1)

    return 1;

  else

    return n * (n - 1);

}

 

extern "C"

int fact(int n)

{

    TestFact t;

    return t.fact(n);

}

將代碼存爲wrapper.cpp不用寫python接口封裝, 直接編譯成so庫,

 

g++ -fPIC wrapper.cpp -o example.so -shared -I/usr/include/python2.6 -I/usr/lib/python2.6/config

 

 

 

進入python, 能夠以下使用

 

>>> import ctypes

>>> pdll = ctypes.CDLL('/home/ubuntu/tmp/example.so')

>>> pdll.fact(4)

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