C++ 嵌入 Python3 -==- 2

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1. C++ 嵌入 Python3 -==- 2

下面我们让情况在复杂一点

1.1 在c++里面执行一段 Python 脚本

1.2 从c++往Python传递数据，Python计算的结果返回给C++

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2. 上程序把，注释我写好点

来自于Python3 文档里面的例子，稍微改动了一点点

// pyD.cpp : 定义控制台应用程序的入口点。

//

#include "stdafx.h"

#include "Python.h"

// 下面的例子。来自于帮助文档，让我们先原汁原味

int main(int argc, char* argv[])

{

//--===========================================---

Py_Initialize();

//--===========================================---

//5.1. Very High Level Embedding -- 直接执行一段Python语句

/*

相当于在Python里面执行 图1

from time import time,ctime

print('today is',ctime(time()))

*/

PyRun_SimpleString("from time import time,ctime \n"

"print('today is',ctime(time())) \n");

/* 5.2 Pure Embedding

文档说的很明确

To show this, consider what the extension code from Python to C really does:

Convert data values from Python to C,

从Python往C传递数据

Perform a function call to a C routine using the converted values, and

Convert the data values from the call from C to Python.

When embedding Python, the interface code does:

Convert data values from C to Python,

从C往Python传递数据

Perform a function call to a Python interface routine using the converted values, and

Convert the data values from the call from Python to C.

*/

PyObject *pName, *pModule, *pDict, *pFunc;

PyObject *pArgs, *pValue;

int i;

if (argc < 3) {

fprintf(stderr,"Usage: call pythonfile funcname [args]\n");

return 1;

}

Py_Initialize();

pName = PyUnicode_FromString(argv[1]);

/* Error checking of pName left out */

pModule = PyImport_Import(pName);

Py_DECREF(pName);

if (pModule != NULL) {

//--==得到第三个参数， 就是那个multiply==--

pFunc = PyObject_GetAttrString(pModule, argv[2]);

/* pFunc is a new reference */

printf("function name is %s \n", argv[2]);

// 得到参数元组

if (pFunc && PyCallable_Check(pFunc)) {

pArgs = PyTuple_New(argc - 3);

for (i = 0; i < argc - 3; ++i) {

pValue = PyLong_FromLong(atoi(argv[i + 3]));

if (!pValue) {

Py_DECREF(pArgs);

Py_DECREF(pModule);

fprintf(stderr, "Cannot convert argument\n");

return 1;

}

/* pValue reference stolen here: */

PyTuple_SetItem(pArgs, i, pValue);

}

//--====call multiply function=====--

// 这里从C往Python 传

pValue = PyObject_CallObject(pFunc, pArgs);

Py_DECREF(pArgs);

if (pValue != NULL) {

int iPythonRet = PyLong_AsLong(pValue);

printf("Result of call: %ld\n", PyLong_AsLong(pValue));

Py_DECREF(pValue);

}

else {

Py_DECREF(pFunc);

Py_DECREF(pModule);

PyErr_Print();

fprintf(stderr,"Call failed\n");

return 1;

}

}

else {

if (PyErr_Occurred())

PyErr_Print();

fprintf(stderr, "Cannot find function \"%s\"\n", argv[2]);

}

Py_XDECREF(pFunc);

Py_DECREF(pModule);

}

else {

PyErr_Print();

fprintf(stderr, "Failed to load \"%s\"\n", argv[1]);

return 1;

}

//--===========================================---

Py_Finalize();

//--===========================================---

return 0;

}

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思考的问题：

增加一个add方法，你应该怎么做？ 减法呢？

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总结一下:

1. 得到模块名字

Py_Initialize();

pName = PyString_FromString(argv[1]);

/* Error checking of pName left out */

pModule = PyImport_Import(pName);

2.得到函数名字

pFunc = PyObject_GetAttrString(pModule, argv[2]);

/* pFunc is a new reference */

if (pFunc && PyCallable_Check(pFunc))

{

...

}

Py_XDECREF(pFunc);

3.调用函数并传递参数

pValue = PyObject_CallObject(pFunc, pArgs);

4.必须完成的清理工作

Py_Finalize();

附上我测试的Python脚本

###########################################################

#

#

# iQSRobots Research

# 使用范围:Python3 + T4

#

#

__filename__= "Hello.py"

__author__ = "Eagle Zhao(eaglezzb@gmail.com"

__version__ = "$Revision: 1.0 $"

__date__ = "$Date: 2011/11/15 21:57:19 $"

__copyright__ = "Copyright (c) 2011 Eagle"

__license__ = "iQS"

###########################################################

def HelloPyhton3():

print("Hello, Python3.2.2!")

def multiply(a,b):

print("Will compute", a, "times", b)

c = 0

for i in range(0, a):

c = c + b

return c

def add(a, b):

return (a+b)

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