"locale" --- 國際化服務
***********************

**原始碼：**Lib/locale.py

======================================================================

The "locale" module opens access to the POSIX locale database and
functionality. The POSIX locale mechanism allows programmers to deal
with certain cultural issues in an application, without requiring the
programmer to know all the specifics of each country where the
software is executed.

The "locale" module is implemented on top of the "_locale" module,
which in turn uses an ANSI C locale implementation if available.

The "locale" module defines the following exception and functions:

exception locale.Error

   Exception raised when the locale passed to "setlocale()" is not
   recognized.

locale.setlocale(category, locale=None)

   If *locale* is given and not "None", "setlocale()" modifies the
   locale setting for the *category*. The available categories are
   listed in the data description below. *locale* may be a string, or
   a pair, language code and encoding. An empty string specifies the
   user's default settings. If the modification of the locale fails,
   the exception "Error" is raised. If successful, the new locale
   setting is returned.

   If *locale* is a pair, it is converted to a locale name using the
   locale aliasing engine. The language code has the same format as a
   locale name, but without encoding and "@"-modifier. The language
   code and encoding can be "None".

   If *locale* is omitted or "None", the current setting for
   *category* is returned.

   範例：

      >>> import locale
      >>> loc = locale.setlocale(locale.LC_ALL)  # get current locale
      # use German locale; name and availability varies with platform
      >>> locale.setlocale(locale.LC_ALL, 'de_DE.UTF-8')
      >>> locale.strcoll('f\xe4n', 'foo')  # compare a string containing an umlaut
      >>> locale.setlocale(locale.LC_ALL, '')   # use user's preferred locale
      >>> locale.setlocale(locale.LC_ALL, 'C')  # use default (C) locale
      >>> locale.setlocale(locale.LC_ALL, loc)  # restore saved locale

   "setlocale()" is not thread-safe on most systems. Applications
   typically start with a call of:

      import locale
      locale.setlocale(locale.LC_ALL, '')

   This sets the locale for all categories to the user's default
   setting (typically specified in the "LANG" environment variable).
   If the locale is not changed thereafter, using multithreading
   should not cause problems.

locale.localeconv()

   Returns the database of the local conventions as a dictionary. This
   dictionary has the following strings as keys:

   +------------------------+---------------------------------------+----------------------------------+
   | 分類                   | Key                                   | 含義                             |
   |========================|=======================================|==================================|
   | "LC_NUMERIC"           | "'decimal_point'"                     | Decimal point character.         |
   +------------------------+---------------------------------------+----------------------------------+
   |                        | "'grouping'"                          | Sequence of numbers specifying   |
   |                        |                                       | which relative positions the     |
   |                        |                                       | "'thousands_sep'" is expected.   |
   |                        |                                       | If the sequence is terminated    |
   |                        |                                       | with "CHAR_MAX", no further      |
   |                        |                                       | grouping is performed. If the    |
   |                        |                                       | sequence terminates with a "0",  |
   |                        |                                       | the last group size is           |
   |                        |                                       | repeatedly used.                 |
   +------------------------+---------------------------------------+----------------------------------+
   |                        | "'thousands_sep'"                     | Character used between groups.   |
   +------------------------+---------------------------------------+----------------------------------+
   | "LC_MONETARY"          | "'int_curr_symbol'"                   | International currency symbol.   |
   +------------------------+---------------------------------------+----------------------------------+
   |                        | "'currency_symbol'"                   | Local currency symbol.           |
   +------------------------+---------------------------------------+----------------------------------+
   |                        | "'p_cs_precedes/n_cs_precedes'"       | Whether the currency symbol      |
   |                        |                                       | precedes the value (for positive |
   |                        |                                       | resp. negative values).          |
   +------------------------+---------------------------------------+----------------------------------+
   |                        | "'p_sep_by_space/n_sep_by_space'"     | Whether the currency symbol is   |
   |                        |                                       | separated from the value  by a   |
   |                        |                                       | space (for positive resp.        |
   |                        |                                       | negative values).                |
   +------------------------+---------------------------------------+----------------------------------+
   |                        | "'mon_decimal_point'"                 | Decimal point used for monetary  |
   |                        |                                       | values.                          |
   +------------------------+---------------------------------------+----------------------------------+
   |                        | "'frac_digits'"                       | Number of fractional digits used |
   |                        |                                       | in local formatting of monetary  |
   |                        |                                       | values.                          |
   +------------------------+---------------------------------------+----------------------------------+
   |                        | "'int_frac_digits'"                   | Number of fractional digits used |
   |                        |                                       | in international formatting of   |
   |                        |                                       | monetary values.                 |
   +------------------------+---------------------------------------+----------------------------------+
   |                        | "'mon_thousands_sep'"                 | Group separator used for         |
   |                        |                                       | monetary values.                 |
   +------------------------+---------------------------------------+----------------------------------+
   |                        | "'mon_grouping'"                      | Equivalent to "'grouping'", used |
   |                        |                                       | for monetary values.             |
   +------------------------+---------------------------------------+----------------------------------+
   |                        | "'positive_sign'"                     | Symbol used to annotate a        |
   |                        |                                       | positive monetary value.         |
   +------------------------+---------------------------------------+----------------------------------+
   |                        | "'negative_sign'"                     | Symbol used to annotate a        |
   |                        |                                       | negative monetary value.         |
   +------------------------+---------------------------------------+----------------------------------+
   |                        | "'p_sign_posn/n_sign_posn'"           | The position of the sign (for    |
   |                        |                                       | positive resp. negative values), |
   |                        |                                       | see below.                       |
   +------------------------+---------------------------------------+----------------------------------+

   All numeric values can be set to "CHAR_MAX" to indicate that there
   is no value specified in this locale.

   The possible values for "'p_sign_posn'" and "'n_sign_posn'" are
   given below.

   +----------------+-------------------------------------------+
   | Value          | Explanation                               |
   |================|===========================================|
   | "0"            | Currency and value are surrounded by      |
   |                | parentheses.                              |
   +----------------+-------------------------------------------+
   | "1"            | The sign should precede the value and     |
   |                | currency symbol.                          |
   +----------------+-------------------------------------------+
   | "2"            | The sign should follow the value and      |
   |                | currency symbol.                          |
   +----------------+-------------------------------------------+
   | "3"            | The sign should immediately precede the   |
   |                | value.                                    |
   +----------------+-------------------------------------------+
   | "4"            | The sign should immediately follow the    |
   |                | value.                                    |
   +----------------+-------------------------------------------+
   | "CHAR_MAX"     | Nothing is specified in this locale.      |
   +----------------+-------------------------------------------+

   The function temporarily sets the "LC_CTYPE" locale to the
   "LC_NUMERIC" locale or the "LC_MONETARY" locale if locales are
   different and numeric or monetary strings are non-ASCII. This
   temporary change affects other threads.

   在 3.7 版的變更: The function now temporarily sets the "LC_CTYPE"
   locale to the "LC_NUMERIC" locale in some cases.

locale.nl_langinfo(option)

   Return some locale-specific information as a string.  This function
   is not available on all systems, and the set of possible options
   might also vary across platforms.  The possible argument values are
   numbers, for which symbolic constants are available in the locale
   module.

   The "nl_langinfo()" function accepts one of the following keys.
   Most descriptions are taken from the corresponding description in
   the GNU C library.

   locale.CODESET

      Get a string with the name of the character encoding used in the
      selected locale.

   locale.D_T_FMT

      Get a string that can be used as a format string for
      "time.strftime()" to represent date and time in a locale-
      specific way.

   locale.D_FMT

      Get a string that can be used as a format string for
      "time.strftime()" to represent a date in a locale-specific way.

   locale.T_FMT

      Get a string that can be used as a format string for
      "time.strftime()" to represent a time in a locale-specific way.

   locale.T_FMT_AMPM

      Get a format string for "time.strftime()" to represent time in
      the am/pm format.

   locale.DAY_1
   locale.DAY_2
   locale.DAY_3
   locale.DAY_4
   locale.DAY_5
   locale.DAY_6
   locale.DAY_7

      Get the name of the n-th day of the week.

      備註:

        This follows the US convention of "DAY_1" being Sunday, not
        the international convention (ISO 8601) that Monday is the
        first day of the week.

   locale.ABDAY_1
   locale.ABDAY_2
   locale.ABDAY_3
   locale.ABDAY_4
   locale.ABDAY_5
   locale.ABDAY_6
   locale.ABDAY_7

      Get the abbreviated name of the n-th day of the week.

   locale.MON_1
   locale.MON_2
   locale.MON_3
   locale.MON_4
   locale.MON_5
   locale.MON_6
   locale.MON_7
   locale.MON_8
   locale.MON_9
   locale.MON_10
   locale.MON_11
   locale.MON_12

      Get the name of the n-th month.

   locale.ABMON_1
   locale.ABMON_2
   locale.ABMON_3
   locale.ABMON_4
   locale.ABMON_5
   locale.ABMON_6
   locale.ABMON_7
   locale.ABMON_8
   locale.ABMON_9
   locale.ABMON_10
   locale.ABMON_11
   locale.ABMON_12

      Get the abbreviated name of the n-th month.

   locale.RADIXCHAR

      Get the radix character (decimal dot, decimal comma, etc.).

   locale.THOUSEP

      Get the separator character for thousands (groups of three
      digits).

   locale.YESEXPR

      Get a regular expression that can be used with the regex
      function to recognize a positive response to a yes/no question.

   locale.NOEXPR

      Get a regular expression that can be used with the "regex(3)"
      function to recognize a negative response to a yes/no question.

      備註:

        The regular expressions for "YESEXPR" and "NOEXPR" use syntax
        suitable for the "regex" function from the C library, which
        might differ from the syntax used in "re".

   locale.CRNCYSTR

      Get the currency symbol, preceded by "-" if the symbol should
      appear before the value, "+" if the symbol should appear after
      the value, or "." if the symbol should replace the radix
      character.

   locale.ERA

      Get a string which describes how years are counted and displayed
      for each era in a locale.

      Most locales do not define this value.  An example of a locale
      which does define this value is the Japanese one.  In Japan, the
      traditional representation of dates includes the name of the era
      corresponding to the then-emperor's reign.

      Normally it should not be necessary to use this value directly.
      Specifying the "E" modifier in their format strings causes the
      "time.strftime()" function to use this information. The format
      of the returned string is specified in *The Open Group Base
      Specifications Issue 8*, paragraph 7.3.5.2 LC_TIME C-Language
      Access.

   locale.ERA_D_T_FMT

      Get a format string for "time.strftime()" to represent date and
      time in a locale-specific era-based way.

   locale.ERA_D_FMT

      Get a format string for "time.strftime()" to represent a date in
      a locale-specific era-based way.

   locale.ERA_T_FMT

      Get a format string for "time.strftime()" to represent a time in
      a locale-specific era-based way.

   locale.ALT_DIGITS

      Get a string consisting of up to 100 semicolon-separated symbols
      used to represent the values 0 to 99 in a locale-specific way.
      In most locales this is an empty string.

   The function temporarily sets the "LC_CTYPE" locale to the locale
   of the category that determines the requested value ("LC_TIME",
   "LC_NUMERIC", "LC_MONETARY" or "LC_MESSAGES") if locales are
   different and the resulting string is non-ASCII. This temporary
   change affects other threads.

   在 3.14 版的變更: The function now temporarily sets the "LC_CTYPE"
   locale in some cases.

locale.getdefaultlocale([envvars])

   Tries to determine the default locale settings and returns them as
   a tuple of the form "(language code, encoding)".

   According to POSIX, a program which has not called
   "setlocale(LC_ALL, '')" runs using the portable "'C'" locale.
   Calling "setlocale(LC_ALL, '')" lets it use the default locale as
   defined by the "LANG" variable.  Since we do not want to interfere
   with the current locale setting we thus emulate the behavior in the
   way described above.

   To maintain compatibility with other platforms, not only the "LANG"
   variable is tested, but a list of variables given as envvars
   parameter.  The first found to be defined will be used.  *envvars*
   defaults to the search path used in GNU gettext; it must always
   contain the variable name "'LANG'".  The GNU gettext search path
   contains "'LC_ALL'", "'LC_CTYPE'", "'LANG'" and "'LANGUAGE'", in
   that order.

   The language code has the same format as a locale name, but without
   encoding and "@"-modifier. The language code and encoding may be
   "None" if their values cannot be determined. The "C" locale is
   represented as "(None, None)".

   自從版本 3.11 後不推薦使用，將會自版本 3.15 中移除。.

locale.getlocale(category=LC_CTYPE)

   Returns the current setting for the given locale category as a
   tuple containing the language code and encoding. *category* may be
   one of the "LC_*" values except "LC_ALL".  It defaults to
   "LC_CTYPE".

   The language code has the same format as a locale name, but without
   encoding and "@"-modifier. The language code and encoding may be
   "None" if their values cannot be determined. The "C" locale is
   represented as "(None, None)".

locale.getpreferredencoding(do_setlocale=True)

   Return the *locale encoding* used for text data, according to user
   preferences.  User preferences are expressed differently on
   different systems, and might not be available programmatically on
   some systems, so this function only returns a guess.

   On some systems, it is necessary to invoke "setlocale()" to obtain
   the user preferences, so this function is not thread-safe. If
   invoking setlocale is not necessary or desired, *do_setlocale*
   should be set to "False".

   On Android or if the Python UTF-8 Mode is enabled, always return
   "'utf-8'", the *locale encoding* and the *do_setlocale* argument
   are ignored.

   The Python preinitialization configures the LC_CTYPE locale. See
   also the *filesystem encoding and error handler*.

   在 3.7 版的變更: The function now always returns ""utf-8"" on
   Android or if the Python UTF-8 Mode is enabled.

locale.getencoding()

   Get the current *locale encoding*:

   * On Android and VxWorks, return ""utf-8"".

   * On Unix, return the encoding of the current "LC_CTYPE" locale.
     Return ""utf-8"" if "nl_langinfo(CODESET)" returns an empty
     string: for example, if the current LC_CTYPE locale is not
     supported.

   * On Windows, return the ANSI code page.

   The Python preinitialization configures the LC_CTYPE locale. See
   also the *filesystem encoding and error handler*.

   This function is similar to "getpreferredencoding(False)" except
   this function ignores the Python UTF-8 Mode.

   在 3.11 版被加入.

locale.normalize(localename)

   Returns a normalized locale code for the given locale name.  The
   returned locale code is formatted for use with "setlocale()".  If
   normalization fails, the original name is returned unchanged.

   If the given encoding is not known, the function defaults to the
   default encoding for the locale code just like "setlocale()".

locale.strcoll(string1, string2)

   Compares two strings according to the current "LC_COLLATE" setting.
   As any other compare function, returns a negative, or a positive
   value, or "0", depending on whether *string1* collates before or
   after *string2* or is equal to it.

locale.strxfrm(string)

   Transforms a string to one that can be used in locale-aware
   comparisons.  For example, "strxfrm(s1) < strxfrm(s2)" is
   equivalent to "strcoll(s1, s2) < 0".  This function can be used
   when the same string is compared repeatedly, e.g. when collating a
   sequence of strings.

locale.format_string(format, val, grouping=False, monetary=False)

   Formats a number *val* according to the current "LC_NUMERIC"
   setting. The format follows the conventions of the "%" operator.
   For floating-point values, the decimal point is modified if
   appropriate.  If *grouping* is "True", also takes the grouping into
   account.

   If *monetary* is true, the conversion uses monetary thousands
   separator and grouping strings.

   Processes formatting specifiers as in "format % val", but takes the
   current locale settings into account.

   在 3.7 版的變更: 新增了 *monetary* 關鍵字參數。

locale.currency(val, symbol=True, grouping=False, international=False)

   Formats a number *val* according to the current "LC_MONETARY"
   settings.

   The returned string includes the currency symbol if *symbol* is
   true, which is the default. If *grouping* is "True" (which is not
   the default), grouping is done with the value. If *international*
   is "True" (which is not the default), the international currency
   symbol is used.

   備註:

     This function will not work with the 'C' locale, so you have to
     set a locale via "setlocale()" first.

locale.str(float)

   Formats a floating-point number using the same format as the built-
   in function "str(float)", but takes the decimal point into account.

locale.delocalize(string)

   Converts a string into a normalized number string, following the
   "LC_NUMERIC" settings.

   在 3.5 版被加入.

locale.localize(string, grouping=False, monetary=False)

   Converts a normalized number string into a formatted string
   following the "LC_NUMERIC" settings.

   在 3.10 版被加入.

locale.atof(string, func=float)

   Converts a string to a number, following the "LC_NUMERIC" settings,
   by calling *func* on the result of calling "delocalize()" on
   *string*.

locale.atoi(string)

   Converts a string to an integer, following the "LC_NUMERIC"
   conventions.

locale.LC_CTYPE

   Locale category for the character type functions.  Most
   importantly, this category defines the text encoding, i.e. how
   bytes are interpreted as Unicode codepoints.  See **PEP 538** and
   **PEP 540** for how this variable might be automatically coerced to
   "C.UTF-8" to avoid issues created by invalid settings in containers
   or incompatible settings passed over remote SSH connections.

   Python doesn't internally use locale-dependent character
   transformation functions from "ctype.h". Instead, "pyctype.h"
   provides locale-independent equivalents like "Py_TOLOWER".

locale.LC_COLLATE

   Locale category for sorting strings.  The functions "strcoll()" and
   "strxfrm()" of the "locale" module are affected.

locale.LC_TIME

   Locale category for the formatting of time.  The function
   "time.strftime()" follows these conventions.

locale.LC_MONETARY

   Locale category for formatting of monetary values.  The available
   options are available from the "localeconv()" function.

locale.LC_MESSAGES

   Locale category for message display. Python currently does not
   support application specific locale-aware messages.  Messages
   displayed by the operating system, like those returned by
   "os.strerror()" might be affected by this category.

   This value may not be available on operating systems not conforming
   to the POSIX standard, most notably Windows.

locale.LC_NUMERIC

   Locale category for formatting numbers.  The functions
   "format_string()", "atoi()", "atof()" and "str()" of the "locale"
   module are affected by that category.  All other numeric formatting
   operations are not affected.

locale.LC_ALL

   Combination of all locale settings.  If this flag is used when the
   locale is changed, setting the locale for all categories is
   attempted. If that fails for any category, no category is changed
   at all.  When the locale is retrieved using this flag, a string
   indicating the setting for all categories is returned. This string
   can be later used to restore the settings.

locale.CHAR_MAX

   This is a symbolic constant used for different values returned by
   "localeconv()".


Background, details, hints, tips and caveats
============================================

The C standard defines the locale as a program-wide property that may
be relatively expensive to change.  On top of that, some
implementations are broken in such a way that frequent locale changes
may cause core dumps.  This makes the locale somewhat painful to use
correctly.

Initially, when a program is started, the locale is the "C" locale, no
matter what the user's preferred locale is.  There is one exception:
the "LC_CTYPE" category is changed at startup to set the current
locale encoding to the user's preferred locale encoding. The program
must explicitly say that it wants the user's preferred locale settings
for other categories by calling "setlocale(LC_ALL, '')".

It is generally a bad idea to call "setlocale()" in some library
routine, since as a side effect it affects the entire program.  Saving
and restoring it is almost as bad: it is expensive and affects other
threads that happen to run before the settings have been restored.

If, when coding a module for general use, you need a locale
independent version of an operation that is affected by the locale
(such as certain formats used with "time.strftime()"), you will have
to find a way to do it without using the standard library routine.
Even better is convincing yourself that using locale settings is okay.
Only as a last resort should you document that your module is not
compatible with non-"C" locale settings.

The only way to perform numeric operations according to the locale is
to use the special functions defined by this module: "atof()",
"atoi()", "format_string()", "str()".

There is no way to perform case conversions and character
classifications according to the locale.  For (Unicode) text strings
these are done according to the character value only, while for byte
strings, the conversions and classifications are done according to the
ASCII value of the byte, and bytes whose high bit is set (i.e., non-
ASCII bytes) are never converted or considered part of a character
class such as letter or whitespace.


Locale names
============

The format of the locale name is platform dependent, and the set of
supported locales can depend on the system configuration.

On Posix platforms, it usually has the format [1]:

     language ["_" territory] ["." charset] ["@" modifier]

where *language* is a two- or three-letter language code from ISO 639,
*territory* is a two-letter country or region code from ISO 3166,
*charset* is a locale encoding, and *modifier* is a script name, a
language subtag, a sort order identifier, or other locale modifier
(for example, "latin", "valencia", "stroke" and "euro").

On Windows, several formats are supported. [2] [3] A subset of IETF
BCP 47 tags:

     language ["-" script] ["-" territory] ["." charset]
     language ["-" script] "-" territory "-" modifier

where *language* and *territory* have the same meaning as in Posix,
*script* is a four-letter script code from ISO 15924, and *modifier*
is a language subtag, a sort order identifier or custom modifier (for
example, "valencia", "stroke" or "x-python"). Both hyphen ("'-'") and
underscore ("'_'") separators are supported. Only UTF-8 encoding is
allowed for BCP 47 tags.

Windows also supports locale names in the format:

     language ["_" territory] ["." charset]

where *language* and *territory* are full names, such as "English" and
"United States", and *charset* is either a code page number (for
example, "1252") or UTF-8. Only the underscore separator is supported
in this format.

The "C" locale is supported on all platforms.

[1] IEEE Std 1003.1-2024; 8.2 Internationalization Variables

[2] UCRT Locale names, Languages, and Country/Region strings

[3] Locale Names


For extension writers and programs that embed Python
====================================================

Extension modules should never call "setlocale()", except to find out
what the current locale is.  But since the return value can only be
used portably to restore it, that is not very useful (except perhaps
to find out whether or not the locale is "C").

When Python code uses the "locale" module to change the locale, this
also affects the embedding application.  If the embedding application
doesn't want this to happen, it should remove the "_locale" extension
module (which does all the work) from the table of built-in modules in
the "config.c" file, and make sure that the "_locale" module is not
accessible as a shared library.


Access to message catalogs
==========================

locale.gettext(msg)

locale.dgettext(domain, msg)

locale.dcgettext(domain, msg, category)

locale.textdomain(domain)

locale.bindtextdomain(domain, dir)

locale.bind_textdomain_codeset(domain, codeset)

The locale module exposes the C library's gettext interface on systems
that provide this interface.  It consists of the functions
"gettext()", "dgettext()", "dcgettext()", "textdomain()",
"bindtextdomain()", and "bind_textdomain_codeset()".  These are
similar to the same functions in the "gettext" module, but use the C
library's binary format for message catalogs, and the C library's
search algorithms for locating message catalogs.

Python applications should normally find no need to invoke these
functions, and should use "gettext" instead.  A known exception to
this rule are applications that link with additional C libraries which
internally invoke C functions "gettext" or "dcgettext".  For these
applications, it may be necessary to bind the text domain, so that the
libraries can properly locate their message catalogs.
