On Tue, Feb 2, 2021 at 8:16 PM Victor Stinner <vstin...@python.org> wrote: > > > > I understand that encoding=locale.get_locale_encoding() would be > > > different from encoding="locale": > > > encoding=locale.get_locale_encoding() doesn't call > > > os.device_encoding(), right? > > > > > > > Yes. > > Would it be useful to add a io.get_locale_encoding(fd)->str (maybe > "get_default_encoding"?) function which gives the chosen encoding from > a file descriptor, similar to open(fd, encoding="locale").encoding? > The os.device_encoding() call is not obvious. >
I don't think it's so useful. encoding=None is 99% same to encoding=locale.getpreferedencoding(False). On Unix, os.device_encoding() just returns locale encoding. On Windows, os.device_encoding() is very unlikely used. open() uses WindowsConsoleIO for console unless PYTHONLEGACYWINDOWSSTDIO is set and encoding for it is UTF-8. And that's why I removed the detailed behavior from the PEP. It is too detailed and almost unrelated to EncodingWarning. I wrote a simple comment in this section instead. https://www.python.org/dev/peps/pep-0597/#locale-is-not-a-codec-alias > > > > > Opt-in warning > > > > --------------- > > > > > > > > Although ``DeprecationWarning`` is suppressed by default, emitting > > > > ``DeprecationWarning`` always when ``encoding`` option is omitted > > > > would be too noisy. > > > > > > The PEP is not very clear. Does "-X warn_encoding" only emits the > > > warning, or does it also display it by default? Does it add a warning > > > filter for EncodingWarning? > > > > > > > This section is not the spec. This section is the rationale for adding > > EncodingWarning instead of using DeprecationWarning. > > > > As spec saying, EncodingWarning is a subclass of Warning. So it is > > displayed by default. But it is not emitted by default. > > > > When -X encoding_warning (or -X warn_default_encoding) is used, the > > warning is emitted and shown unless the user suppresses warnings. > > I understand that EncodingWarning is always displayed by default > (default warning filters don't ignore it, whereas DeprecationWarning > are ignored by default), but no warning is emitted by default. Ok, > that makes sense. Maybe try to say it explicitly in the PEP. > > > > This PEP doesn't have "backward compatibility" section because the PEP > > doesn't break any backward compatibility. > > IMO it's a good thing to always have the section, just to say that you > took time to think about backward compatibility ;-) The section can be > empty, like just say "there is no incompatible change" ;-) > > > > And if developers want to support Python ~3.9 and use -X > > warn_default_encoding on 3.10, they need to write > > `encoding=getattr(io, "LOCALE_ENCODING", None)`, as written in the > > spec. > > Maybe repeat it in the Backward Compatibility section. > > It's important to provide a way to prevent the warning without losing > the support for old Python versions. > will do. > > > > The main question is if it's possible to use encoding="locale" on > > > Python 3.6-3.9 (maybe using some ugly hacks). > > > > No. > > Hum. To write code compatible with Python 3.9, I understand that > encoding=None is the closest to encoding="locale". > > And I understand that encoding=getattr(io, "LOCALE_ENCODING", None) is > backward and forward compatible ;-) > > Well, encoding=None will hopefully remain accepted with your PEP > anyway for lazy developers ;-) > Yes. I don't think this warning is enabled by default in near future. So developers can just use the option to find missing `encoding="utf-8"` bug. > > > Oh, I'm sorry. I want to make it in 3.10. > > Since it doesn't change anything by default, the warning is only > displayed when you opt-in for it, IMO Python 3.10 target is > reasonable. > > Victor > -- > Night gathers, and now my watch begins. It shall not end until my death. -- Inada Naoki <songofaca...@gmail.com> _______________________________________________ Python-Dev mailing list -- python-dev@python.org To unsubscribe send an email to python-dev-le...@python.org https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived at https://mail.python.org/archives/list/python-dev@python.org/message/FZ567UQIEKO5IIVSQPUFCSZJOZBMYD4D/ Code of Conduct: http://python.org/psf/codeofconduct/
