Is it possible to call a Python module from ObjC?

Question

Using PyObjC, is it possible to import a Python module, call a function and get the result as (say) a NSString?

For example, doing the equivalent of the following Python code:

import mymodule
result = mymodule.mymethod()

..in pseudo-ObjC:

PyModule *mypymod = [PyImport module:@"mymodule"];
NSString *result = [[mypymod getattr:"mymethod"] call:@"mymethod"];

Answer 1

Not quite, AFAIK, but you can do it "the C way", as suggested for example in http://lists.apple.com/archives/Cocoa-dev/2004/Jan/msg00598.html -- or "the Pyobjc way" as per http://osdir.com/ml/python.pyobjc.devel/2005-06/msg00019.html (see also all other messages on that thread for further clarification).

Answer 2

As mentioned in Alex Martelli's answer (although the link in the mailing-list message was broken, it should be http://www.python.org/doc/2.5.1/ext/pure-embedding.html).. The C way of calling..

print urllib.urlopen("http://google.com").read()

• Add the Python.framework to your project (Right click External Frameworks.., Add > Existing Frameworks. The framework in in /System/Library/Frameworks/
• Add /System/Library/Frameworks/Python.framework/Headers to your "Header Search Path" (Project > Edit Project Settings)

The following code should work (although it's probably not the best code ever written..)

#include <Python.h>

int main(){
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
    Py_Initialize();

    // import urllib
    PyObject *mymodule = PyImport_Import(PyString_FromString("urllib"));
    // thefunc = urllib.urlopen
    PyObject *thefunc = PyObject_GetAttrString(mymodule, "urlopen");

    // if callable(thefunc):
    if(thefunc && PyCallable_Check(thefunc)){
        // theargs = ()
        PyObject *theargs = PyTuple_New(1);

        // theargs[0] = "http://google.com"
        PyTuple_SetItem(theargs, 0, PyString_FromString("http://google.com"));

        // f = thefunc.__call__(*theargs)
        PyObject *f = PyObject_CallObject(thefunc, theargs);

        // read = f.read
        PyObject *read = PyObject_GetAttrString(f, "read");

        // result = read.__call__()
        PyObject *result = PyObject_CallObject(read, NULL);


        if(result != NULL){
            // print result
            printf("Result of call: %s", PyString_AsString(result));
        }
    }
    [pool release];
}

Also this tutorial is good