Events

A receiver that can be made ready directly.

Usage

There are cases where it is useful to be able to send a signal to a select() loop, for example, to stop a loop from outside the loop itself.

To do that, you can use an Event receiver and call set() on it when you want to make it ready.

Stopping

The receiver will be re-activated (will keep blocking) after the current set event is received. To stop the receiver completely, you can call stop().

Example

Exit after printing the first 5 numbers

import asyncio

from frequenz.channels import Anycast, select, selected_from
from frequenz.channels.event import Event

channel: Anycast[int] = Anycast(name="channel")
receiver = channel.new_receiver()
sender = channel.new_sender()
stop_event = Event(name="stop")


async def do_work() -> None:
    async for selected in select(receiver, stop_event):
        if selected_from(selected, receiver):
            print(selected.message)
        elif selected_from(selected, stop_event):
            print("Stop event triggered")
            stop_event.stop()
            break


async def send_stuff() -> None:
    for i in range(10):
        if stop_event.is_stopped:
            break
        await asyncio.sleep(1)
        await sender.send(i)


async def main() -> None:
    async with asyncio.TaskGroup() as task_group:
        task_group.create_task(do_work(), name="do_work")
        task_group.create_task(send_stuff(), name="send_stuff")
        await asyncio.sleep(5.5)
        stop_event.set()


asyncio.run(main())