Trio Cheatsheet

trio_cheatcheet.md

Trio Cheatsheet

N. P. O'Donnell, 2021

Simple Trio Program

import trio


async def main():
    print("hello")


trio.run(main)

Sleeping

To sleep, use trio.sleep:

async def main():
    trio.sleep(3.)
    print("hello after 3s")

Nurseries

Nurseries are used for running multiple tasks:

import trio


async def waiter(sleep_s):
    await trio.sleep(sleep_s)
    print(f"done waiting {sleep_s}s")


async def main():
    print("about to wait...")
    async with trio.open_nursery() as n:
        n.start_soon(waiter, 3)
        n.start_soon(waiter, 5)
        print("waiting...")
    print("all done")


trio.run(main)

Implementing Timeouuts

Timeouts can be implemented using move_on_after:

async def main():
    with trio.move_on_after(6.):
        await waiter(3.)
        await waiter(2.)
        print("got everything done")
    print("moving on")

Timeout with Failure

Use fail_after to raise an exception if a task does not complete on time:

async def main():
    try:
        with trio.fail_after(4.):
            async with trio.open_nursery() as n:
                n.start_soon(waiter, 3.)
                n.start_soon(waiter, 5.)
        print("didn't fail!")
    except trio.TooSlowError as e:
        print("failed")