Errors

Exception groups (PEP 654, 3.11) allow multiple exceptions to be raised together and handled selectively. TaskGroup uses them when several concurrent tasks fail.

try:
    async with asyncio.TaskGroup() as tg:
        tg.create_task(fetch(a))
        tg.create_task(fetch(b))
except* TimeoutError as eg:
    ...
except* ValueError as eg:
    ...

Conventions in common use:

• One base exception class per package, with specific subclasses beneath it, so callers catch package-level errors rather than the errors of transitive dependencies.
• Wrap third-party exceptions at the boundary where they are raised, preserving the original with raise ... from err.
• contextlib.suppress(SpecificError) for intentional ignores, rather than a bare except: pass, which also swallows KeyboardInterrupt and SystemExit.
• add_note() (3.11) to attach context to an exception without wrapping it.

References

• PEP 654 – Exception Groups and except* — Final, 3.11.