What is the problem with `PySet_Contains` when calling Py func in C? [duplicate]

There were several problems with your code:

1. Py_Initialize() was not called.
2. PyImport_ImportModule() failed to find your python file, since in embedded Python you start without an initial module, relative to which the search can work. The fix is to explicitly include the current directory in sys.path.
3. "(O)" in Py_BuildValue() should use a capital 'O'.
4. The printlist function should return a value (since that is what the C-code expects).

This should work:

main.c

#include <Python.h>

void initPython()
{
    Py_Initialize();
    PyObject *sysmodule = PyImport_ImportModule("sys");
    PyObject *syspath = PyObject_GetAttrString(sysmodule, "path");
    PyList_Append(syspath, PyString_FromString("."));
    Py_DECREF(syspath);
    Py_DECREF(sysmodule);
}

int callModuleFunc(int array[], size_t size) {
    PyObject *mymodule = PyImport_ImportModule("py_function");
    assert(mymodule != NULL);
    PyObject *myfunc = PyObject_GetAttrString(mymodule, "printlist");
    assert(myfunc != NULL);
    PyObject *mylist = PyList_New(size);
    for (size_t i = 0; i != size; ++i) {
        PyList_SET_ITEM(mylist, i, PyInt_FromLong(array[i]));
    }
    PyObject *arglist = Py_BuildValue("(O)", mylist);
    assert(arglist != NULL);
    PyObject *result = PyObject_CallObject(myfunc, arglist);
    assert(result != NULL);
    int retval = (int)PyInt_AsLong(result);
    Py_DECREF(result);
    Py_DECREF(arglist);
    Py_DECREF(mylist);
    Py_DECREF(myfunc);
    Py_DECREF(mymodule);
    return retval;
}

int main(int argc, char *argv[])
{
    initPython();

    int a[] = {1,2,3,4,5,6,7};
    callModuleFunc(a, 4);
    callModuleFunc(a+2, 5);

    Py_Finalize();
    return 0;
}

py_function.py

'''py_function.py - Python source designed to '''
'''demonstrate the use of python embedding'''

def printlist(mylist):
    print mylist
    return 0