Python asyncio 问题

    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