PyScript asyncio porting

August 17, 2026 · View on GitHub

Who: You want an existing pydevices-examples example to run in the browser via PyScript.

Prerequisites: PyScript local setup. Read Events concept first.

Why asyncio?

PyScript's runtime is asyncio-based. A typical MCU example:

def main():
    while True:
        for event in runtime.poll():
            handle(event)
        display.show()

main()

This blocks the browser event loop. PyScript needs async def, await, and yields to the scheduler.

Port pattern

from board_config import display_drv
from app_runtime import runtime
from multimer import asyncio

async def main():
    while True:
        for event in runtime.poll():
            ...  # handle event
        display_drv.show()
        await asyncio.sleep(0)  # yield to the event loop

runtime.run_async(main)

Prefer subscribe + keep-alive when you do not need a custom async main:

runtime.on(runtime.events.MOUSEBUTTONDOWN, handle)
runtime.run_forever()

If runtime.poll() is synchronous, call it inside the async loop and await a yield each iteration so touch redraw and timers run. Import the portable event-loop module with from multimer import asyncio, then use await asyncio.sleep(0).

For periodic callbacks, use multimer.AsyncTimer inside async def main() after the loop is running.

Examples to study

Script	What to copy
`calc_graphics.py`	Full async UI loop
`eventsys_simpletest.py`	Minimal poll + await
`paint.py`	Touch drawing with asyncio

Try via: .site/pyscript/micropython.html?modules=eventsys_simpletest

Minimal shell (no query string): open async.html — a bouncing square that yields with await asyncio.sleep(0.016).

Common failures

Symptom	Cause
Frozen tab	Blocking loop, no `await`
No touch response	Poll loop never yields
Import error	Example needs packages not in `micropython.toml` manifest

Regenerate manifest after adding examples: ./scripts/install_refresh_manifests.sh.

Reference

pydevices product source