Python調用C/C++的種種方法

Python是解釋性語言, 底層就是用c實現的, 所以用python調用C是很容易的, 下面就總結一下各種調用的方法, 給出例子, 所有例子都在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

然後在有此so庫的目錄, 進入python, 可以如下使用

import example

example.fact(4)

 ```

2. Python 調用 C++ (base)

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

include

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



然後在有此so庫的目錄, 進入python, 可以如下使用

import example

example.fact(4)

“`

1. Python 調用 C++ (Boost.Python)

Boost庫是非常強大的庫, 其中的python庫可以用來封裝c++被python調用, 功能比較強大, 不但可以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, 並且必須加-lboost_python-gcc42-mt-1_34_1, 這個庫名不一定是這個, 去/user/lib查

然後在有此so庫的目錄, 進入python, 可以如下使用

>>> 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, 可以如下使用

>>> import ctypes
>>> pdll = ctypes.CDLL('/home/ubuntu/tmp/example.so')
>>> pdll.fact(4)
12