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Diffstat (limited to 'Doc/whatsnew/3.7.rst')
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diff --git a/Doc/whatsnew/3.7.rst b/Doc/whatsnew/3.7.rst index 3df3093..6074781 100644 --- a/Doc/whatsnew/3.7.rst +++ b/Doc/whatsnew/3.7.rst @@ -70,6 +70,51 @@ Summary -- Release highlights New Features ============ +.. _whatsnew37-pep538: + +PEP 538: Legacy C Locale Coercion +--------------------------------- + +An ongoing challenge within the Python 3 series has been determining a sensible +default strategy for handling the "7-bit ASCII" text encoding assumption +currently implied by the use of the default C locale on non-Windows platforms. + +:pep:`538` updates the default interpreter command line interface to +automatically coerce that locale to an available UTF-8 based locale as +described in the documentation of the new :envvar:`PYTHONCOERCECLOCALE` +environment variable. Automatically setting ``LC_CTYPE`` this way means that +both the core interpreter and locale-aware C extensions (such as +:mod:`readline`) will assume the use of UTF-8 as the default text encoding, +rather than ASCII. + +The platform support definition in :pep:`11` has also been updated to limit +full text handling support to suitably configured non-ASCII based locales. + +As part of this change, the default error handler for ``stdin`` and ``stdout`` +is now ``surrogateescape`` (rather than ``strict``) when using any of the +defined coercion target locales (currently ``C.UTF-8``, ``C.utf8``, and +``UTF-8``). The default error handler for ``stderr`` continues to be +``backslashreplace``, regardless of locale. + +.. note:: + + In the current implementation, a warning message is printed directly to + ``stderr`` even for successful implicit locale coercion. This gives + redistributors and system integrators the opportunity to determine if they + should be making an environmental change to avoid the need for implicit + coercion at the Python interpreter level. + + However, it's not clear that this is going to be the best approach for + the final 3.7.0 release, and we may end up deciding to disable the warning + by default and provide some way of opting into it at runtime or build time. + + Concrete examples of use cases where it would be preferrable to disable the + warning by default can be noted on :issue:`30565`. + +.. seealso:: + + :pep:`538` -- Coercing the legacy C locale to a UTF-8 based locale + PEP written and implemented by Nick Coghlan. Other Language Changes |