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

[Donald Stufft]

> On Nov 19, 2017, at 8:40 AM, Nathaniel Smith <njs at pobox.com> wrote:
> 
> We have been using DeprecationWarning for changes where code will
> transition from working -> raising an error, and that *is* based on
> the Official Recommendation to hide those by default whenever
> possible. We've been doing this for a few years now, and I'd say our
> experience so far has been... poor. I'm trying to figure out how to
> say this politely. Basically it doesn't work at all. What happens in
> practice is that we issue a DeprecationWarning for a year, mostly
> no-one notices, then we make the change in a 1.x.0 release, everyone's
> code breaks, we roll it back in 1.x.1, and then possibly repeat
> several times in 1.(x+1).0 and 1.(x+2).0 until enough people have
> updated their code that the screams die down. I'm pretty sure we'll be
> changing our policy at some point, possibly to always use
> FutureWarning for everything.


In pip we ended up working around the not-displaying-by-default so that we got the old behavior back again because hiding warnings doesn’t work great in my experience.
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