[Python-Dev] PEP 538 warning at startup: please remove it (original) (raw)

Nick Coghlan ncoghlan at gmail.com
Tue Jun 13 02:51:23 EDT 2017

On 13 June 2017 at 06:58, Gregory P. Smith <greg at krypto.org> wrote:

I guess so. It is a system environment configuration problem. But I'd still imagine that end users never touch their LANG or LC* environment variables themselves. (the only time I touch anything is to explicitly set LANG=C on occasion when I want text process shell tools to run a lot faster; but I hardly count as I live in ascii-land, aka the US)

I'm inclined to suggest it should be silent, but I'm curious if we can get some linux distros testing with it enabled during the beta period to see how much impact it actually has on users in the real world. We could be talking about a minor non-issue.

It's at least affecting Fedora's build system (where we've backported PEP 538 to the system Python in F26): https://lists.fedorahosted.org/archives/list/python-devel@lists.fedoraproject.org/thread/VSEGOF76XMBJOAO4C2MORNK3I2VIPOTU/

However, Fedora python-devel's current view on that is that it's a sign that the build system's configuration is outdated, and we should be setting the locale to C.UTF-8 instead. (Ditto for the Fedora Docker images, which are currently expecting systemd to sort out the default locale settings, so it ends up being left as the C default when there's no init system running inside the container).

So I think the most compelling argument in favour of making the warning silent by default is Victor's one: so that "LANG=C python" "just works", rather than attempting to persuade end users to change what they've become accustomed to typing in order to get software to emit otherwise internationalised text in English.

After all, one of the long term goals of PEP 538 is to get to the point where at least the glibc developers, and hopefully other C standard library implementation developers, are comfortable having UTF-8 as the default text encoding anyway, at which point CPython's locale coercion would essentially become a no-op (and folks would have to type something like "LANG=C.ASCII" or "LANG=C.latin-1" to get the old platform dependent non-UTF-8 behaviour back).

If we turned the warning off by default, but retained an easy "on-switch" for the warning to help track places where locale coercion is triggering unexpectedly (e.g. "PYTHONCOERCECLOCALE=warn"), that would probably give us the best of both worlds.

Cheers, Nick.

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

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