Python中time.sleep(0.001)是否真的只等待1毫秒

import time

while True:
    st = time.time()
    time.sleep(0.001)
    et = time.time()
    print('dt={dt}'.format(dt=et - st))

        no_frame_time = 0
        while True:
            if self._stop:
                logger.info(f"xxxx stop.")
                break

            if self._pause:
                time.sleep(0.01)
                continue

            if len(self.msg_deque) == 0:
                st = time.time()
                time.sleep(0.001)
                # no_frame_time += 0.001 # 这写法由于sleep不准确，导致最早no_frame_time与实际值误差特别大
                et = time.time() - st
                no_frame_time += et  # 此处是累积时间
                if no_frame_time > 1:
                    logging.warning("xxxx not arrived in last second.")
                    self.fps_signal.emit(0)
                    no_frame_time = 0
                continue
            else:
                no_frame_time = 0
            
            # ... 省略任务主体