MultiError examples from my 2017 python language summit talk (slides: https://vorpus.org/~njs/misc/trio-language-summit-2017.pdf)

multierrer.py

import trio

async def main():
    async with trio.open_nursery() as nursery:
        nursery.spawn(f1)
        nursery.spawn(f2)

async def f1():
    raise KeyError

async def f2():
    async with trio.open_nursery() as nursery:
        nursery.spawn(f2a)
        nursery.spawn(f2b)

async def f2a():
    raise ValueError

async def f2b():
    raise RuntimeError

trio.run(main)

multierror-catch.py

import trio

async def main():
    def handler(exc):
        if isinstance(exc, (RuntimeError, KeyError)):
            return None
        else:
            return exc
    with trio.MultiError.catch(handler):
        async with trio.open_nursery() as nursery:
            nursery.spawn(f1)
            nursery.spawn(f2)

async def f1():
    raise KeyError

async def f2():
    async with trio.open_nursery() as nursery:
        nursery.spawn(f2a)
        nursery.spawn(f2b)

async def f2a():
    raise ValueError

async def f2b():
    raise RuntimeError

trio.run(main)