Show progress when downloading data from S3

[mturoci]

This snippet shows how to update Wave UI with a current s3 download progress.

This code requires boto3 to be installed.

from h2o_wave import main, app, Q, ui
import boto3
import asyncio

class Progress:
    def __init__(self) -> None:
        self.val = 0

    def get(self):
        return self.val

    def update_progress(self, progress):
        self.val = self.val + progress


progress = Progress()
total_size = 7840516

def download():
    def update(val):
        progress.update_progress(val)

    boto3.resource('s3').Bucket('h2o-wave').download_file('releases/h2o_wave-0.20.0-py3-none-win_amd64.whl', 'hello.whl', Callback=update)

async def update_ui(q: Q):
    q.page['controls'] = ui.form_card(box='1 1 2 2', items=[
        ui.progress(label='Download', value=progress.get() / 7840516, caption=f'Downloaded {progress.get()} / {total_size} bytes'),
    ])
    await q.page.save()

async def poll(q: Q):
    while progress.get() < total_size:
        await update_ui(q)
        await q.sleep(0.2)
    await update_ui(q)


@app('/')
async def serve(q: Q):
    if not q.client.initialized:
        q.page['controls'] = ui.form_card(box='1 1 2 2', items=[
            ui.button(name='download', label='Download')
        ])
        q.client.initialized = True

    if q.args.download:
        poll_future = asyncio.ensure_future(poll(q))

        await q.run(download)
        await poll_future

    await q.page.save()

Thanks @geomodular for consultation.