Best Practice for Running Background Tasks on Page Load

[patrickwasp]

Question

I have a NiceGUI app where I need to run a CPU-intensive task when a page loads, without blocking the UI. Here's my current solution using ui.timer:

import time

from nicegui import run, ui


def heavy_computation(work_length: int):
    time.sleep(work_length)
    return "Done!"


class PageExample:
    def __init__(self, work_length: int) -> None:
        self.work_length = work_length

    def create(self):
        ui.label(f"Hello World, work length: {self.work_length}")

        with ui.tabs().classes("w-full") as tabs:
            one = ui.tab("One")
            two = ui.tab("Two")
        with ui.tab_panels(tabs, value=two).classes("w-full"):
            with ui.tab_panel(one):
                ui.label("First tab")

            with ui.tab_panel(two):
                ui.label("Second tab")

        self.spinner = ui.spinner(size="lg")
        self.spinner.visible = False

        ui.timer(0, self.run_heavy_computation, once=True)

    async def run_heavy_computation(self):
        print("Running heavy computation")
        self.spinner.visible = True
        result = await run.cpu_bound(heavy_computation, work_length=self.work_length)
        self.spinner.visible = False
        ui.notify(result)


@ui.page("/{work_length}")
def index_page(work_length: int):
    example_page = PageExample(work_length=work_length)
    example_page.create()


ui.run()

While this works, I'm wondering if using ui.timer(0, ...) is the best practice for running background tasks on page load.

[rodja]

There is an undocumented module background_tasks in NiceGUI:

from nicegui import ui, background_tasks

def heavy_computation():
    time.sleep(2)

@ui.page('/')
def index():
    async def compute():
        await run.cpu_bound(heavy_computation)
        spinner.visible = False

    spinner = ui.spinner()
    background_tasks.create(compute())

ui.run()