RuntimeError: 此事件循环已在运行 |使用 discord.py 时出错答案

【问题标题】：RuntimeError: This event loop is already running | Error while using discord.pyRuntimeError: 此事件循环已在运行 |使用 discord.py 时出错
【发布时间】：2021-09-19 10:40:22
【问题描述】：

我正在尝试在 mcoc.py cog 中发出命令 -

    @commands.command()
    async def mcoc(self, ctx, tier_str:int,*,champname:str):  
        champname = champname.strip()
        champname = champname.lower()
        if champname == "bwcv":
            champname=="blackwidow_timely"
        url = f"https://auntm.ai/champions/{champname}/tier/{tier_str}"
                                                                                                                           
        session = AsyncHTMLSession()
        
        r = await session.get(url)
        
        await r.html.render(sleep=1, keep_page=True, scrolldown=1)
        
        information = await r.html.find("div.sc-hiSbYr.XqbgT")
        sig = await r.html.find('div.sc-fbNXWD.iFMyOV')
        name = await r.html.find('div.sc-cxFLnm.izBVou')
        tier_access = information[0]
        self.tier = tier_access.text
async with ctx.typing:
            embed = discord.Embed(title=f"{self.name_of_champ}",description=f"More Information about {self.name_of_champ} can be found (here)[{self.url_page}]")
            await ctx.send(embed=embed)

但我不断收到错误-

Ignoring exception in on_command_error
Traceback (most recent call last):
  File "/home/indo/.local/lib/python3.9/site-packages/discord/ext/commands/core.py", line 85, in wrapped
    ret = await coro(*args, **kwargs)
  File "/home/indo/Documents/Python/LoB/cogs/mcoc.py", line 119, in mcoc
    await r.html.render(sleep=1, keep_page=True, scrolldown=1)
  File "/home/indo/.local/lib/python3.9/site-packages/requests_html.py", line 598, in render
    content, result, page = self.session.loop.run_until_complete(self._async_render(url=self.url, script=script, sleep=sleep, wait=wait, content=self.html, reload=reload, scrolldown=scrolldown, timeout=timeout, keep_page=keep_page))
  File "/usr/lib/python3.9/asyncio/base_events.py", line 618, in run_until_complete
    self._check_running()
  File "/usr/lib/python3.9/asyncio/base_events.py", line 578, in _check_running
    raise RuntimeError('This event loop is already running')
RuntimeError: This event loop is already running

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/home/indo/.local/lib/python3.9/site-packages/discord/ext/commands/core.py", line 94, in wrapped
    raise CommandInvokeError(exc) from exc
discord.ext.commands.errors.CommandInvokeError: Command raised an exception: RuntimeError: This event loop is already running

即使在继续尝试之后，我仍然收到错误，这是什么原因以及如何解决这个问题？

【问题讨论】：

错误消息提到使用run_until_complete。 Python 的默认 asyncio 库不允许这种类型的嵌套循环，即只能运行一个事件循环。此循环被 discord.py 占用，因此任何设置自己的循环的库都与 discord.py 不兼容。不过可能有一种解决方法。
发现 this question 和 this library 但由于 discord.py 和 requests_html 都是第三方软件包，我怀疑这些是否适用于您的情况。
@Nevus 那么我该怎么做才能让它运行呢？
我尝试了一个nest_asyncio，但那个没有用:(
它是第一个运行的东西吗？我不是专家，但似乎任何解决方案充其量都是猴子补丁。您可能必须切换库才能使其正常工作。

标签： python asynchronous discord.py runtime python-asyncio

【解决方案1】：

解决错误，这似乎是特定于 Jupyter Notebook 和 Jupyter Lab 的， 这样做：

pip install nest_asyncio

您的 python 应用中可能还需要这个

import nest_asyncio
nest_asyncio.apply()

完整的补丁信息参考：

https://github.com/psf/requests-html/issues/402

https://github.com/erdewit/nest_asyncio

【讨论】：