def crawl(self, tasks: list, task_handler=None, callback=None, semaphore_count=100):         if not task_handler:             task_handler = self.page_handler          main_loop = asyncio.new_event_loop()         asyncio.set_event_loop(main_loop)         semaphore = asyncio.Semaphore(semaphore_count)         n = len(tasks)          asyncio.set_event_loop_policy(uvloop.EventLoopPolicy())          new_tasks = []          async def _run():             async with semaphore:                 async with ClientSession() as session:                     for i, task in enumerate(tasks):                         future = asyncio.ensure_future(task_handler(task, i=i + 1, n=n, session=session))                         if callback:                             future.add_done_callback(callback)                         new_tasks.append(future)                     return await asyncio.gather(*new_tasks)          try:             result = main_loop.run_until_complete(_run())             return [x for j in result for x in j]         except Exception as e:             logging.exception(e)         finally:             if not main_loop.is_closed():                 main_loop.close()             return []                  async def page_handler(self, task, session, **kwargs):         ''' 省略部分代码 '''         result = self.crawl(book_item_url_list, self.item_handler)         return result  

• 怎样创建一个唯一 ClientSession()

  • session = ClientSession() 这样不好使

• 在 page_handler 再次条用 crawl 出现

  • Cannot run the event loop while another loop is running
  • crawl 里面的任务会在产生子任务， 这个子任务如何用 loop 加入任务列表

• 我传了 callback 又用了 return 这是不是又点矛盾

• 我打印 i/n 这个 i 是乱序 怎样任务列表顺序执行