254 – asyncio events

The module asyncio provides the class Event that you can use to synchronise multiple asyncio tasks.

You can create an event by simply instantiating the class:

from asyncio import Event

local_files_ready = Event()

The event can now be awaited in your code if you use the method wait:

async def process_local_files():
    await local_files_ready.wait()
    ... # Process the files locally

The await only concludes once the event is set elsewhere by using the method set:

async def download_files():
    ... # Download the files
    local_files_ready.set()
    ... # Keep doing other stuff

Like with any other synchronisation primitive, you have to be careful about deadlocks.