examples/background.py

# Background Tasks
# Use q.run() to execute functions in the background, in-process.
# #background_tasks
# ---
import time
import random
from h2o_wave import main, app, Q, ui


def blocking_function(secs) -> str:
    time.sleep(secs)  # Blocks!
    return f'Done waiting for {secs} seconds!'


@app('/demo')
async def serve(q: Q):
    if q.args.start:
        q.page['form'] = ui.form_card(box='1 1 6 2', items=[ui.progress('Running...')])
        await q.page.save()

        seconds = random.randint(1, 6)

        # DON'T DO THIS!
        # This will make your app unresponsive for some time:
        # message = blocking_function(seconds)

        # Do this instead:
        message = await q.run(blocking_function, seconds)

        q.page['form'] = ui.form_card(box='1 1 6 1', items=[ui.message_bar('info', message)])
        await q.page.save()
    else:
        q.page['form'] = ui.form_card(box='1 1 2 1', items=[ui.button(name='start', label='Start')])
        await q.page.save()