1、背景
应该在jupyter中遇到过这种问题：
"RuntimeError: This event loop is already running".
这表示，你在jupyter中使用事件循环会出现无法执行，因为他不允许嵌套，所以可以用下面方式解决。
2、方法
By design asyncio does not allow its event loop to be nested. This presents a practical problem: When in an environment where the event loop is already running it's impossible to run tasks and wait for the result. Trying to do so will give the error "RuntimeError: This event loop is already running".
The issue pops up in various environments, such as web servers, GUI applications and in Jupyter notebooks.
This module patches asyncio to allow nested use of asyncio.run and loop.run_until_complete.
pip3 install nest_asyncio
import nest_asyncio
nest_asyncio.apply()