ui.notify from a background process?

[adarshpunj]

Update: I was able to use ui.refreshable as a hack - however, I'm not sure if this is a good solution.

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Question

Hi,

I'm trying to run a function with ui.notify like this:

def executor(arg):
    response = some_task(arg) # i can't modify this `some_task` callable; can be both io or cpu bound
    if not response:
        ui.notify("Failed successfully")

ui.button("Click me", on_click=lambda: run.io_bound(executor, arg=arg)

This throws:

RuntimeError: The current slot cannot be determined because the slot stack for this task is empty.
This may happen if you try to create UI from a background task.
To fix this, enter the target slot explicitly using `with container_element:`.

I can't do on_click=lambda: executor(arg=arg) as this will block the UI for the time some_task runs.

Normally, I'd use webhooks in cases like this (especially when I'm able to modify the some_task method)

What are some Pythonic solutions to this problem?

[falkoschindler]

Hi @adarshpunj,

The problem is that ui.notify doesn't know which client to notify. There could be multiple pages with multiple connected browsers.

But you can try a similar approach like we do in RoSys:

def notify(message: str) -> None:
    for client in Client.instances.values():
        if not client.has_socket_connection:
            continue
        with client:
            ui.notify(message)

https://github.com/zauberzeug/rosys/blob/c87eb713b4bc7324e78524ae2420a365b7c1b5cb/rosys/rosys.py#L61-L80

This sends the notification to all connected clients.

[adarshpunj]

Thanks for sharing.

What do you think of this solution using ui.refreshable

@ui.refreshable
def notify(msg: str | None) -> None:
    if msg:
        ui.notify(msg)

def executor(arg):
    response = some_task(arg)
    if not response:
        notify.refresh("Failed successfully")

notify(None)

[falkoschindler]

Interesting solution! It might be less intuitive to read, but should work as well. This way you're sending the notification only to the client who called notify(None) in the first place. 👍🏻