[Python-Dev] PEP 460 reboot (original) (raw)

Barry Warsaw barry at python.org
Tue Jan 14 22:26:09 CET 2014

On Jan 14, 2014, at 10:52 AM, Guido van Rossum wrote:

Which reminds me. Quite a few people have spoken out in favor of loud failures rather than silent "wrong" output. But I think that in the specific context of formatting output, there is a long and IMO good tradition of producing (slightly) wrong output in favor of more strict behavior.

In the email package we now have a tradition of allowing either behavior.

http://docs.python.org/3.4/library/email.policy.html#email.policy.Policy.raise_on_defect

Perhaps not appropriate for the PEP 460 related cases, but I think the policy mechanism works great for email parsing, where sometimes you definitely want to fail early (e.g. you are composing new messages out of literal strings) and other times where you are willing to put up with some best-effort representation in exchange for no exceptions being raised (e.g. you are parsing messages being fed to you from your mail server).

-Barry

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