C++调用Python 3.7.0

开发环境：Visual Studio 2015 + Python 3.7.0
一、在C++代码中写Python脚本
在C++中含有调用Python脚本的API函数，在C++代码中嵌入Python脚本代码，是通过PyRun_SimpleString()函数实现。它允许将Python脚本代码写成字符串，作为PyRun_SimpleString()函数参数，从而实现Python脚本的解析与运行，这种方法适用于Python脚本简短的情形，其主要流程如下图所示：

下面通过一则实例演示C++调用Python的这种方式。
（1）C++代码：

#include <iostream>
#include <Python.h>

using namespace std;

int main(int argc, char *argv[])
{
    wchar_t *program = Py_DecodeLocale(argv[0], NULL);
    if (program == NULL) {
        fprintf(stderr, "Fatal error: cannot decode argv[0]\n");
        exit(1);
    }
    //The Py_SetProgramName() function should be called before Py_Initialize()
    //to inform the interpreter about paths to Python run-time libraries 
    Py_SetProgramName(program);  //optional but recommended 
    // the Python interpreter is initialized with Py_Initialize()
    Py_Initialize();            
    //pass a string containing Python statements to PyRun_SimpleString()
    PyRun_SimpleString("from time import time,ctime\n"
                       "print('Today is', ctime(time()))\n"); 
    //the Py_FinalizeEx() call shuts the interpreter down
    if (Py_FinalizeEx() < 0) {  
        exit(120);
    }
    PyMem_RawFree(program);
    //system("pause");
    //return 0;
    return getchar();
}

（2）程序运行结果：

二、C++调用本地Python脚本文件
在很多情形，Python脚本并不是那么简短，在C++代码中直接嵌入Python脚本代码虽然也可以达到需求，但这样的代码往往不易阅读与维护。因此，C++ 中的Python API允许通过加载本地Python脚本文件的方式调用Python。下面通过一则实例演示C++调用Python的这种方式
（1）C++代码：

#include <iostream>
#include <Python.h>
using namespace std;
/*
This code loads a Python script using argv[1], and calls the function named in argv[2].
Its integer arguments are the other values of the argv array.
*/
int main(int argc, char *argv[])
{
    PyObject *pName, *pModule, *pFunc;
    PyObject *pArgs, *pValue;

    if (argc < 3) 
    {
        fprintf(stderr, "Usage: call pythonfile funcname [args]\n");
        return 1;
    }
    // initializing the interpreter
    Py_Initialize();
    pName = PyUnicode_DecodeFSDefault(argv[1]);
    /* Error checking of pName left out */

    // the script is loaded using PyImport_Import()
    pModule = PyImport_Import(pName);
    Py_DECREF(pName);

    if (pModule != NULL) 
    {
        // Once the script is loaded, the name we’re looking for is retrieved using PyObject_GetAttrString()
        pFunc = PyObject_GetAttrString(pModule, argv[2]);
        /* pFunc is a new reference */

        if (pFunc && PyCallable_Check(pFunc)) 
        {
            pArgs = PyTuple_New(argc - 3);
            for (int 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);
            }
            pValue = PyObject_CallObject(pFunc, pArgs);
            Py_DECREF(pArgs);
            if (pValue != NULL) 
            {
                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;
    }
    if (Py_FinalizeEx() < 0) 
    {
        return 120;
    }
    return getchar();
}

（2）Python脚本文件MyMultiply.py代码：

def multiply(a,b):
    print("Will compute", a, "times", b)
    c = 0
    for i in range(0, a):
        c = c + b
    return c

（3）VS命令行参数：

MyMultiply multiply 5 3

（4）程序运行结果：