background_thread.py 文件源码

def start(self):
    """Starts this background thread."""
    if not self._Thread__initialized:
      raise RuntimeError('thread.__init__() not called')
    if self._Thread__started.is_set():
      raise RuntimeError('threads can only be started once')
    with threading._active_limbo_lock:
      threading._limbo[self] = self
    try:
      start_new_background_thread(self.__bootstrap, ())
    except Exception:
      with threading._active_limbo_lock:
        del threading._limbo[self]
      raise
    self._Thread__started.wait()