[capi-sig] C integration with multithreaded Python script

[Andreas Sommer]

Hope this is the right mailing list, please complain if not ;)

I'm currently experimenting with the integration of Python (2.6) scripts 
into my application, and am using the following script for testing:

    *import* threading, time

    *def* handler():
        print("a")
        time.sleep(0.95)
        print("b")

    t = threading.Thread(target = handler)
    t.start()


And in C++, it's this code:

    Py_SetProgramName("test");
    Py_Initialize();
    *if*(!Py_IsInitialized()) *throw* std::exception();


    PyObject *module = PyImport_AddModule("__main__");
    PyObject *dict = PyModule_GetDict(module);

    printf("1\n");

    strcpy(script, "import threading, time\n"
                   "def handler():\n"
                   "    print(\"a\")\n"
                   "    time.sleep(0.95)\n"
                   "    print(\"b\")\n"
                   "t = threading.Thread(target = handler)\n"
                   "t.start()\n");

    PyObject *obj = PyRun_String(script, Py_file_input, dict, dict);
    printf("2\n");


    PyErr_Print();
    Py_Finalize();


When executing, the output is

1
a2

as opposed to the expected

1
a
b
2

It seems to me that when the main execution path (after t.start()) 
finishes, the other thread (called t) is canceled?! Adding t.join() to 
the end of the script gives the expected output, but isn't it possible 
to let PyRun_xxx wait for all remaining threads to end? I know the 
Python interpreter does this, but I didn't get much information from its 
source code (it seems to run scripts with the runpy module).


Best regards