How to get a char* from a PyObject which points to a string

Question

How can I get a char* from a PyObject which points to a string. For example, this is the python script,

Test.Connect("272.22.20.65", 1234)

and this is the C++ code,

static PyObject* Connect(PyObject *self, PyObject *args)
{
    PyObject* pIP;
    PyObject* pPort;

    if (!PyArg_UnpackTuple(args, "Connect", 2, 2, &pIP, &pPort)) 
    {
        return NULL;
    }

    const char* zIP = GetAsString(pIP);
    long iPort      = PyLong_AsLong(pPort);

I want to get that IP address as a char* (GetAsString is a dummy function :D ). Please note that I'm using Python 3.1.

P.S. I don't think this question got the correct answer , since there is no PyStringObject or PyString_AsString in Python 3. Isn't it ?

@Sven Marnach. it is str. But there is no way of getting char* from PyUnicode_*. Am I wrong ? — Morpheus
– Morpheus, Commented Mar 27, 2012 at 19:41
lol...where is Sven Marnach ? When I replied you, your comment was missing — Morpheus
– Morpheus, Commented Mar 27, 2012 at 19:43

Ignacio Vazquez-Abrams · Accepted Answer · 2012-03-27 19:21:10Z

5

First you encode it, then you retrieve it. Don't forget to decref the temporary.

answered Mar 27, 2012 at 19:21

Ignacio Vazquez-Abrams

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4 Comments

Morpheus Over a year ago

Thanks for the answer, but it is not working. PyBytes_AsString is returing a NULL. (in a simplify way this is how I used it, PyBytes_AsString(PyUnicode_AsUTF8String(pObject)) )

Morpheus Over a year ago

@Sven Marnach. Thanks for the point. I'm confused with python3, with python2x it is straightforward, isn't it.

Ignacio Vazquez-Abrams Over a year ago

Calling the two functions together like that will result in a memory leak.

Morpheus Over a year ago

I simplified it for commenting, it is like this. PyObject* pStrObj = PyUnicode_AsUTF8String(pObject); char* zStr = PyBytes_AsString(pStrObj); char* zStrDup = strdup(zStr); Py_DECREF(pStrObj); Hope I did it in correct way.

André Anjos · Accepted Answer · 2014-03-31 07:51:32Z

0

Here is my portable recipe for it, which makes use the default encoding, where that is applicable. It assumes you start with a PyObject*, named o. If you still have your input tuple from the function call, you can skip the first 2 lines.

PyObject* args = Py_BuildValue("(O)", o);
/* Py_DECREF(o); if o is not borrowed */
if (!args) return 0;
const char* s = 0;
if (!PyArg_ParseTuple(args, "s", &s)) {
  Py_DECREF(args);
  return 0;
}

/* s now points to a const char* - use it, delete args when done */

Py_DECREF(args);

PS: I have not tested it, but it should work with older versions of Python as well. There is nothing on it which is version specific.

answered Mar 31, 2014 at 7:51

André Anjos

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