staticPyObject*thread_get_ident(PyObject*self,PyObject*Py_UNUSED(ignored)){PyThread_ident_tident=PyThread_get_thread_ident_ex();// <-- ULLif (ident==PYTHREAD_INVALID_THREAD_ID) {PyErr_SetString(ThreadError,"no current thread ident");returnNULL;    }returnPyLong_FromUnsignedLongLong(ident);}

class_MainThread(Thread):def__init__(self):Thread.__init__(self,name="MainThread",daemon=False)self._started.set()self._ident=_get_main_thread_ident()self._handle=_make_thread_handle(self._ident)if_HAVE_THREAD_NATIVE_ID:self._set_native_id()with_active_limbo_lock:_active[self._ident]=self

staticPyObject*thread__get_main_thread_ident(PyObject*module,PyObject*Py_UNUSED(ignored)){returnPyLong_FromUnsignedLongLong(_PyRuntime.main_thread);}

/* Platform-specific identifier and PyThreadState, respectively, for the       main thread in the main interpreter. */unsigned longmain_thread;

// Set it to the ID of the main thread of the main interpreter.runtime->main_thread=PyThread_get_thread_ident();

>>> import threading>>> ct = threading.current_thread()>>> ct<_DummyThread(Dummy-1, started daemon 18446744072483979068)>>>> hex(ct.ident)'0xffffffffb6f33f3c'>>> main = threading.main_thread()>>> hex(main.ident)'0xb6f33f3c'>>> main._set_ident()>>> hex(main.ident)'0xffffffffb6f33f3c'

def current_thread():    """Return the current Thread object, corresponding to the caller's thread of control.    If the caller's thread of control was not created through the threading    module, a dummy thread object with limited functionality is returned.    """    try:        return _active[get_ident()]    except KeyError:        return _DummyThread()