[Python-ideas] [Python-Dev] PEP 3156 - Asynchronous IO Support Rebooted

[Richard Oudkerk]

On 09/01/2013 2:31am, Nick Coghlan wrote:
> The exception() method exists for the same reason that we support both
> "key in mapping" and raising KeyError from "mapping[key]": sometimes
> you want "Look Before You Leap", other times you want to let the
> exception fly. If you want the latter, just call .result() directly,
> if you want the former, check .exception() first.

But how can you do LBYL.  I can't see a way to check that an exception 
has occurred seeing whether result() raises an error: done() tells you 
that the operation is finished, but not whether it succeeded.

-- 
Richard