创建并通过C API从字符串调用Python函数 [英] Create and call python function from string via C API

问题描述

是否有可能从字符串加载一个Python函数，然后调用带参数的功能，得到返回值？

我使用Python C API从我的C ++应用程序内部运行蟒蛇code。我能够加载使用 PyImport_Import 文件的模块，从得到一个函数对象使用 PyObject_GetAttrString ，和调用具有 PyObject_CallObject 的功能。我想要做的就是从一个字符串，而不是一个文件加载模块/功能。有一些相当于 PyImport_Import 这将让我传递一个字符串，而不是一个文件？我需要将参数传递给我打电话的功能，我需要访问返回值，所以我不能只用 PyRun_SimpleString 。

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修改

我发现越来越转向到 PyRun_String 后，此解决方案。我创建一个新的模块，获得的字典对象，通过沿中调用 PyRun_String 在我的新模块来定义一个函数，然后让一个函数对象中通过 PyObject_CallObject 新创建的函数，并调用它，传递我的ARGS。这是我找到了解决我的问题：
的main.cpp

 
诠释的main（）
{
    *的PyObject PNAME，* pModule，* pArgs，* P值，* pFunc;
    的PyObject * pGlobal = PyDict_New（）;
    *的PyObject pLocal;    //创建一个新的模块对象
    的PyObject * pNewMod = PyModule_New（mymod）;    Py_Initialize（）;
    PyModule_AddStringConstant（pNewMod__file__，）;    //从我模块获取字典对象，所以我可以把它传递给PyRun_String
    pLocal = PyModule_GetDict（pNewMod）;    //定义我的函数新创建的模块中
    P值= PyRun_String（DEF等等（X）：\\ n \\ t打印5 * X \\ n \\ treturn 77 \\ n，Py_file_input，pGlobal，pLocal）;
    Py_DECREF（P值）;    //获取函数我只是定义一个指针
    pFunc = PyObject_GetAttrString（pNewMod，嗒嗒）;    //建立一个元组来保存我的论点（只是4号在这种情况下）
    pArgs = PyTuple_New（1）;
    P值= PyInt_FromLong（4）;
    PyTuple_SetItem（pArgs，0，P值）;    //调用我的函数，它传递数字四
    P值= PyObject_CallObject（pFunc，pArgs）;
    Py_DECREF（pArgs）;
    的printf（返回VAL：％ld个\\ N，PyInt_AsLong（P值））;
    Py_DECREF（P值）;    Py_XDECREF（pFunc）;
    Py_DECREF（pNewMod）;
    Py_Finalize（）;    返回0;
}
 

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这是我原来的职位的休息，为后人留下了：

下面是我最初做的：
的main.cpp ：

 
＃包括LT＆; Python.h>诠释的main（）
{
    *的PyObject PNAME，* pModule，* pArgs，* P值，* pFunc;    Py_Initialize（）;
    PyRun_SimpleString（进口SYS）;
    PyRun_SimpleString（sys.path.append（''））;
    PNAME = PyString_FromString（ATEST）;
    pModule = PyImport_Import（PNAME）;
    Py_DECREF（PNAME）;    如果（pModule == NULL）
    {
        的printf（PMOD为空\\ n）;
        PyErr_Print（）;
        返回1;
    }    pFunc = PyObject_GetAttrString（pModuledoStuff）;
    pArgs = PyTuple_New（1）;
    P值= PyInt_FromLong（4）;
    PyTuple_SetItem（pArgs，0，P值）;    P值= PyObject_CallObject（pFunc，pArgs）;
    Py_DECREF（pArgs）;
    的printf（返回VAL：％ld个\\ N，PyInt_AsLong（P值））;
    Py_DECREF（P值）;    Py_XDECREF（pFunc）;
    Py_DECREF（pModule）;    Py_Finalize（）;    返回0;
}
 

和 atest.py ：

 
高清doStuff（X）：
    打印X为％d \\ n％X
    返回2 * X
 

解决方案

PyRun_String Python的C API的可能是你在找什么。请参阅： http://docs.python.org/c-api/veryhigh.html

Is it possible to load a python function from a string and then call that function with arguments and get the return value?

I'm using the python C API to run python code from inside my C++ application. I'm able to load a module from a file using PyImport_Import, get a function object from that using PyObject_GetAttrString, and call the function with PyObject_CallObject. What I'd like to do is to load the module/function from a string instead of a file. Is there some equivalent to PyImport_Import which would allow me to pass it a string instead of a file? I need to pass arguments to the function I'm calling and I need access to the return value, so I can't just use PyRun_SimpleString.

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Edit:

I found this solution after getting turned on to PyRun_String. I'm creating a new module, getting its dictionary object, passing that along in a call to PyRun_String to define a function in my new module, then getting a function object for that newly created function and calling it via PyObject_CallObject, passing my args. This is what I've found to solve my problem: main.cpp

int main()
{
    PyObject *pName, *pModule, *pArgs, *pValue, *pFunc;
    PyObject *pGlobal = PyDict_New();
    PyObject *pLocal;

    //Create a new module object
    PyObject *pNewMod = PyModule_New("mymod");

    Py_Initialize();
    PyModule_AddStringConstant(pNewMod, "__file__", "");

    //Get the dictionary object from my module so I can pass this to PyRun_String
    pLocal = PyModule_GetDict(pNewMod);

    //Define my function in the newly created module
    pValue = PyRun_String("def blah(x):\n\tprint 5 * x\n\treturn 77\n", Py_file_input, pGlobal, pLocal);
    Py_DECREF(pValue);

    //Get a pointer to the function I just defined
    pFunc = PyObject_GetAttrString(pNewMod, "blah");

    //Build a tuple to hold my arguments (just the number 4 in this case)
    pArgs = PyTuple_New(1);
    pValue = PyInt_FromLong(4);
    PyTuple_SetItem(pArgs, 0, pValue);

    //Call my function, passing it the number four
    pValue = PyObject_CallObject(pFunc, pArgs);
    Py_DECREF(pArgs);
    printf("Returned val: %ld\n", PyInt_AsLong(pValue));
    Py_DECREF(pValue);

    Py_XDECREF(pFunc);
    Py_DECREF(pNewMod);
    Py_Finalize();

    return 0;
}

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Here is the rest of my original post, left for posterity:

Here's what I was doing originally: main.cpp:

#include <Python.h>

int main()
{
    PyObject *pName, *pModule, *pArgs, *pValue, *pFunc;

    Py_Initialize();
    PyRun_SimpleString("import sys");
    PyRun_SimpleString("sys.path.append('')");
    pName = PyString_FromString("atest");
    pModule = PyImport_Import(pName);
    Py_DECREF(pName);

    if(pModule == NULL)
    {
        printf("PMod is null\n");
        PyErr_Print();
        return 1;
    }

    pFunc = PyObject_GetAttrString(pModule, "doStuff");
    pArgs = PyTuple_New(1);
    pValue = PyInt_FromLong(4);
    PyTuple_SetItem(pArgs, 0, pValue);

    pValue = PyObject_CallObject(pFunc, pArgs);
    Py_DECREF(pArgs);
    printf("Returned val: %ld\n", PyInt_AsLong(pValue));
    Py_DECREF(pValue);

    Py_XDECREF(pFunc);
    Py_DECREF(pModule);

    Py_Finalize();

    return 0;
}

And atest.py:

def doStuff( x):
    print "X is %d\n" % x
    return 2 * x

解决方案

PyRun_String in the Python C API is probably what you're looking for. See: http://docs.python.org/c-api/veryhigh.html

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