A highly opinionated flake8 plugin for Trio-related problems.

pip install flake8-trio==22.9.2



A highly opinionated flake8 plugin for Trio-related problems.

This can include anything from outright bugs, to pointless/dead code, to likely performance issues, to minor points of idiom that might signal a misunderstanding.

It may well be too noisy for anyone with different opinions, that's OK.

Pairs well with flake8-async and flake8-bugbear.


pip install flake8-trio

List of warnings

  • TRIO100: a with trio.fail_after(...): or with trio.move_on_after(...): context does not contain any await statements. This makes it pointless, as the timeout can only be triggered by a checkpoint.
  • TRIO101: yield inside a nursery or cancel scope is only safe when implementing a context manager - otherwise, it breaks exception handling.
  • TRIO102: it's unsafe to await inside finally: or except BaseException/trio.Cancelled unless you use a shielded cancel scope with a timeout.
  • TRIO103: except BaseException and except trio.Cancelled with a code path that doesn't re-raise. Note that any raise statements in loops are ignored since it's tricky to parse loop flow with break, continue and/or the zero-iteration case.
  • TRIO104: Cancelled and BaseException must be re-raised - when a user tries to return or raise a different exception.
  • TRIO105: Calling a trio async function without immediately awaiting it.
  • TRIO106: trio must be imported with import trio for the linter to work.
  • TRIO107: exit or return from async function with no guaranteed checkpoint or exception since function definition.
  • TRIO108: exit, yield or return from async iterable with no guaranteed checkpoint since possible function entry (yield or function definition) Checkpoints are await, async for, and async with (on one of enter/exit).
  • TRIO109: Async function definition with a timeout parameter - use trio.[fail/move_on]_[after/at] instead
  • TRIO110: while <condition>: await trio.sleep() should be replaced by a trio.Event.