C-extension not threadable?

[Marcus Stojek]

>Yes, the Global Interpreter Lock (GIL). When C code runs that was
>invoked from Python code, it holds the GIL, and only one such C code
>can run at any time. So you need to release the lock, using
>Py_BEGIN_ALLOW_THREADS and Py_END_ALLOW_THREADS.
>
>Regards,
>Martin

Never heard about that ;-)
But now its clear and everything works. Very effective answer.
Thanks
Marcus