RuntimeWarning：启用 tracemalloc 以使用 asyncio.sleep 获取对象分配回溯

Posted 2023-03-30

【中文标题】RuntimeWarning：启用 tracemalloc 以使用 asyncio.sleep 获取对象分配回溯

【英文标题】：RuntimeWarning: Enable tracemalloc to get the object allocation traceback with asyncio.sleep

【发布时间】：2019-01-08 08:55:58

【问题描述】：

尝试使用信号量来控制异步请求以控制对目标主机的请求，但我收到以下错误，我认为这意味着我的 asycio.sleep() 实际上并没有在睡觉。我怎样才能解决这个问题？我想为每个目标 URL 的请求添加延迟。

错误：

RuntimeWarning: coroutine 'sleep' was never awaited
Coroutine created at (most recent call last)
  File "sephora_scraper.py", line 71, in <module>
    loop.run_until_complete(main())
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/asyncio/base_events.py", line 571, in run_until_complete
    self.run_forever()
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/asyncio/base_events.py", line 539, in run_forever
    self._run_once()
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/asyncio/base_events.py", line 1767, in _run_once
    handle._run()
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/asyncio/events.py", line 88, in _run
    self._context.run(self._callback, *self._args)
  File "makeup.py", line 26, in get_html
    asyncio.sleep(delay)
  asyncio.sleep(delay)
RuntimeWarning: Enable tracemalloc to get the object allocation traceback

代码：

import sys
import time
import asyncio
import aiohttp

async def get_html(semaphore, session, url, delay=6):
    await semaphore.acquire()
    async with session.get(url) as res:
        html = await res.text()
        asyncio.sleep(delay)
        semaphore.release()
        return html

async def main():
    categories = 
        "makeup": "https://www.sephora.com/shop/"
    
    semaphore = asyncio.Semaphore(value=1)
    tasks = []
    async with aiohttp.ClientSession(loop=loop, connector=aiohttp.TCPConnector(ssl=False)) as session:
        for category, url in categories.items():
                # Get HTML of all pages
            tasks.append(get_html(semaphore, session, url))
        res = await asyncio.gather(*tasks)

if __name__ == "__main__":
    loop = asyncio.get_event_loop()
    loop.run_until_complete(main())

【问题讨论】：

还可以使用async with 或至少try/except 与信号量，如here 所示。它会保证即使出现异常也会释放信号量。

【参考方案1】：

asyncio.sleep(delay)

改成：

await asyncio.sleep(delay)

asyncio.sleep 是 coroutine，应该等待。