[Python-Dev] PEP 565: Show DeprecationWarning in __main__

[Nick Coghlan]

On 6 December 2017 at 06:43, Victor Stinner <victor.stinner at gmail.com> wrote:
> At the end, I'm not sure that the PEP 565 is really needed or would help anyone.

Folks, I'd really appreciate it if you could comment on the merits of
the PEP without implicitly claiming that I don't exist, and that Linux
system administrators don't exist :)

Right now, Linux distro Python library upgrades (including CPython
updates to a new feature release) may result in *hard compatibility
breaks*, as previously deprecated features disappear without warning.

With PEP 565, ad hoc personal scripts will at least get a
DeprecationWarning when APIs they're using are at risk of disappearing
as a result of a distro package or version update. Right now, they
don't get a warning at all.

There is *no way* for any opt in flag to help these users. Now, PEP
565 being rejected wouldn't be the end of the world on that front - we
can apply comparable changes as a downstream patch. However, these
problems aren't unique to Linux, and they aren't unique to any
specific distro: they apply whenever folks are using Python for
personal workflow automation, rather than for redistributable
applications and libraries. So it makes more sense to me to do this
upstream, rather than having the default warnings handling be a
redistributor dependent behaviour.

That said, I go agree we could offer easier to use APIs to app
developers that just want to hide warnings from their users, so I've
filed https://bugs.python.org/issue32229 to propose a straightforward
"warnings.hide_warnings()" API that encapsulates things like checking
for a non-empty sys.warnoptions list.

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia