[capi-sig] C integration with multithreaded Python script

[Andreas Sommer]

I still don't have an answer to this question. Meanwhile I've taken a 
look at the Python interpreter source code and couldn't find out how it 
manages to keep running while other threads exist. Taking the 
/RunModule/ function from the code doesn't help me - same problem: only 
the first few instructions of the background thread are executed and 
then Python execution ends.


Andreas Sommer wrote:
> 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