Python 3.8.2 breaks nest-asyncio

This trivial demo works with CPython 3.8.1 and breaks with 3.8.2:

import asyncio
import nest_asyncio
nest_asyncio.apply()


async def f():
    print("OK")


async def g():
    loop = asyncio.get_event_loop()
    loop.run_until_complete(f())

if __name__ == "__main__":
    asyncio.run(g())

Works

• Linux x64, anaconda, nest_asyncio 1.2.2
• python=3.8.1=h357f687_2 (conda-forge)

Output: OK

Broken

• Linux x64, anaconda, nest_asyncio 1.2.2
• python=3.8.2=h9d8adfe_1_cpython (conda-forge)

Output: RuntimeError: This event loop is already running

[nabobalis]

Just wanted to say I had this issue as well on python 3.8.2 and adding this to my conftest.py worked:

import pytest
import asyncio
import nest_asyncio


@pytest.fixture(scope="session")
def event_loop():
    """
    Don't close event loop at the end of every function decorated by
    @pytest.mark.asyncio
    """
    loop = asyncio.new_event_loop()
    nest_asyncio.apply()
    yield loop
    loop.close()

[gimperiale]

Tested 1.3 vs Python 3.8.2; everything works for me. @gordonwatts pytest-asyncio tampers with the asyncio event loop. I use it too but I was very careful not to mix it with nest-asyncio, uvloop, etc.

Try adding to your conftest.py:

@pytest.fixture(scope="session")
def event_loop():
    """Don't close event loop at the end of every function decorated by
    @pytest.mark.asyncio
    """
    loop = asyncio.new_event_loop()
    yield loop
    loop.close()