gh-91156: Use locale.getencoding() instead of getpreferredencoding (GH-91732)

Co-authored-by: Victor Stinner <vstinner@python.org>

Author: methane

Doc/howto/curses.rst

@@ -299,8 +299,7 @@ The :meth:`~curses.window.addstr` method takes a Python string or
 bytestring as the value to be displayed.  The contents of bytestrings
 are sent to the terminal as-is.  Strings are encoded to bytes using
 the value of the window's :attr:`encoding` attribute; this defaults to
-the default system encoding as returned by
-:func:`locale.getpreferredencoding`.
+the default system encoding as returned by :func:`locale.getencoding`.
 
 The :meth:`~curses.window.addch` methods take a character, which can be
 either a string of length 1, a bytestring of length 1, or an integer.

Doc/library/csv.rst

@@ -542,7 +542,7 @@ The corresponding simplest possible writing example is::
 
 Since :func:`open` is used to open a CSV file for reading, the file
 will by default be decoded into unicode using the system default
-encoding (see :func:`locale.getpreferredencoding`).  To decode a file
+encoding (see :func:`locale.getencoding`).  To decode a file
 using a different encoding, use the ``encoding`` argument of open::
 
    import csv

Doc/library/curses.rst

@@ -27,20 +27,6 @@ Linux and the BSD variants of Unix.
    Whenever the documentation mentions a *character string* it can be specified
    as a Unicode string or a byte string.
 
-.. note::
-
-   Since version 5.4, the ncurses library decides how to interpret non-ASCII data
-   using the ``nl_langinfo`` function.  That means that you have to call
-   :func:`locale.setlocale` in the application and encode Unicode strings
-   using one of the system's available encodings.  This example uses the
-   system's default encoding::
-
-      import locale
-      locale.setlocale(locale.LC_ALL, '')
-      code = locale.getpreferredencoding()
-
-   Then use *code* as the encoding for :meth:`str.encode` calls.
-
 .. seealso::
 
    Module :mod:`curses.ascii`
@@ -923,8 +909,8 @@ the following methods and attributes:
 
    Encoding used to encode method arguments (Unicode strings and characters).
    The encoding attribute is inherited from the parent window when a subwindow
-   is created, for example with :meth:`window.subwin`. By default, the locale
-   encoding is used (see :func:`locale.getpreferredencoding`).
+   is created, for example with :meth:`window.subwin`.
+   By default, current locale encoding is used (see :func:`locale.getencoding`).
 
    .. versionadded:: 3.3
 

Doc/library/functions.rst

@@ -1123,8 +1123,8 @@ are always available.  They are listed here in alphabetical order.
    (which on *some* Unix systems, means that *all* writes append to the end of
    the file regardless of the current seek position).  In text mode, if
    *encoding* is not specified the encoding used is platform-dependent:
-   ``locale.getpreferredencoding(False)`` is called to get the current locale
-   encoding. (For reading and writing raw bytes use binary mode and leave
+   :func:`locale.getencoding()` is called to get the current locale encoding.
+   (For reading and writing raw bytes use binary mode and leave
    *encoding* unspecified.)  The available modes are:
 
    .. _filemodes:
@@ -1183,10 +1183,9 @@ are always available.  They are listed here in alphabetical order.
 
    *encoding* is the name of the encoding used to decode or encode the file.
    This should only be used in text mode.  The default encoding is platform
-   dependent (whatever :func:`locale.getpreferredencoding` returns), but any
-   :term:`text encoding` supported by Python
-   can be used.  See the :mod:`codecs` module for
-   the list of supported encodings.
+   dependent (whatever :func:`locale.getencoding` returns), but any
+   :term:`text encoding` supported by Python can be used.
+   See the :mod:`codecs` module for the list of supported encodings.
 
    *errors* is an optional string that specifies how encoding and decoding
    errors are to be handled—this cannot be used in binary mode.

Doc/library/os.rst

@@ -105,15 +105,15 @@ of the UTF-8 encoding:
 
 * Use UTF-8 as the :term:`filesystem encoding <filesystem encoding and error
   handler>`.
-* :func:`sys.getfilesystemencoding()` returns ``'UTF-8'``.
-* :func:`locale.getpreferredencoding()` returns ``'UTF-8'`` (the *do_setlocale*
+* :func:`sys.getfilesystemencoding()` returns ``'utf-8'``.
+* :func:`locale.getpreferredencoding()` returns ``'utf-8'`` (the *do_setlocale*
   argument has no effect).
 * :data:`sys.stdin`, :data:`sys.stdout`, and :data:`sys.stderr` all use
   UTF-8 as their text encoding, with the ``surrogateescape``
   :ref:`error handler <error-handlers>` being enabled for :data:`sys.stdin`
   and :data:`sys.stdout` (:data:`sys.stderr` continues to use
   ``backslashreplace`` as it does in the default locale-aware mode)
-* On Unix, :func:`os.device_encoding` returns ``'UTF-8'`` rather than the
+* On Unix, :func:`os.device_encoding` returns ``'utf-8'`` rather than the
   device encoding.
 
 Note that the standard stream settings in UTF-8 mode can be overridden by

Lib/test/libregrtest/main.py

@@ -482,8 +482,7 @@ def display_header(self):
         if cpu_count:
             print("== CPU count:", cpu_count)
         print("== encodings: locale=%s, FS=%s"
-              % (locale.getpreferredencoding(False),
-                 sys.getfilesystemencoding()))
+              % (locale.getencoding(), sys.getfilesystemencoding()))
 
     def get_tests_result(self):
         result = []

Lib/test/pythoninfo.py

@@ -155,7 +155,7 @@ def collect_platform(info_add):
 def collect_locale(info_add):
     import locale
 
-    info_add('locale.encoding', locale.getpreferredencoding(False))
+    info_add('locale.getencoding', locale.getencoding())
 
 
 def collect_builtins(info_add):

Lib/test/support/__init__.py

@@ -1445,7 +1445,7 @@ def skip_if_buggy_ucrt_strfptime(test):
     global _buggy_ucrt
     if _buggy_ucrt is None:
         if(sys.platform == 'win32' and
-                locale.getpreferredencoding(False)  == 'cp65001' and
+                locale.getencoding() == 'cp65001' and
                 time.localtime().tm_zone == ''):
             _buggy_ucrt = True
         else:

Lib/test/test__locale.py

@@ -43,7 +43,7 @@ def setUpModule():
                     locale.setlocale(locale.LC_ALL, loc)
                 except Error:
                     continue
-                encoding = locale.getpreferredencoding(False)
+                encoding = locale.getencoding()
                 try:
                     localeconv()
                 except Exception as err:

Lib/test/test_builtin.py

@@ -1204,7 +1204,7 @@ def test_open_default_encoding(self):
                     del os.environ[key]
 
             self.write_testfile()
-            current_locale_encoding = locale.getpreferredencoding(False)
+            current_locale_encoding = locale.getencoding()
             with warnings.catch_warnings():
                 warnings.simplefilter("ignore", EncodingWarning)
                 fp = open(TESTFN, 'w')