Notes¶

I/O in AsyncKivy¶

asynckivy does not have any I/O primitives unlike trio and asyncio do, thus threads may be the best way to perform them without blocking the main-thread:

from concurrent.futures import ThreadPoolExecutor
import asynckivy as ak

executor = ThreadPoolExecutor()


def thread_blocking_operation():
    '''
    This function is called from outside the main-thread so you should not
    perform any graphics-related operations here.
    '''


async def async_fn():
    r = await ak.run_in_thread(thread_blocking_operation)
    print("return value:", r)

    r = await ak.run_in_executor(executor, thread_blocking_operation)
    print("return value:", r)

Unhandled exceptions (not BaseException) are propagated to the caller so you can catch them like you do in synchronous code:

import requests
import asynckivy as ak

async def async_fn(label):
    try:
        response = await ak.run_in_thread(lambda: requests.get('htt...', timeout=10))
    except requests.Timeout:
        label.text = "TIMEOUT!"
    else:
        label.text = "RECEIVED"

Kivy’s Event System¶

(under construction)

The Problem with Async Generators¶

asyncio and trio do some hacky stuff, sys.set_asyncgen_hooks() and sys.get_asyncgen_hooks(), which likely hinders asynckivy-flavored async generators. You can see its details here.

Because of that, the APIs that create async generators might not work perfectly if asyncio or trio is running. Here is a list of them:

Places where async operations are disallowed¶

Most asynckivy APIs that return an async iterator don’t allow async operations during iteration. Here is a list of them:

async for __ in rest_of_touch_events(...):
    await awaitable  # NOT ALLOWED
    async with async_context_manager:  # NOT ALLOWED
        ...
    async for __ in async_iterator:  # NOT ALLOWED
        ...