charliejiangxxx / nest_asyncio Goto Github PK

By design asyncio does not allow its event loop to be nested. This presents a practical problem: in an environment where the event loop is already running, it's impossible to run tasks and wait for the result. Attempting to do so will lead to a "RuntimeError: This event loop is already running".

This issue pops up in various environments, including web servers, GUI applications and in Jupyter notebooks.

This module patches asyncio to enable nested usage of asyncio.run and loop.run_until_complete.

pip3 install nest_asyncio

Python 3.5 or higher is required.

from nest_asyncio import NestedAsyncIO
with NestedAsyncIO():
    ...

Wrap any code requiring nested runs with a NestedAsyncIO context manager or manually call apply and revert on demand. Optionally, a specific loop may be supplied as an as argument to apply or the constructor if you do not wish to patch the the current event loop. An event loop may be patched regardless of its state, running or stopped. Note that this packages is limited to asyncio event loops: general loops from other projects, such as uvloop or quamash, cannot be patched.