2 :mod:`locale` --- Internationalization services
3 ===============================================
6 :synopsis: Internationalization services.
7 .. moduleauthor:: Martin von Löwis <martin@v.loewis.de>
8 .. sectionauthor:: Martin von Löwis <martin@v.loewis.de>
11 The :mod:`locale` module opens access to the POSIX locale database and
12 functionality. The POSIX locale mechanism allows programmers to deal with
13 certain cultural issues in an application, without requiring the programmer to
14 know all the specifics of each country where the software is executed.
16 .. index:: module: _locale
18 The :mod:`locale` module is implemented on top of the :mod:`_locale` module,
19 which in turn uses an ANSI C locale implementation if available.
21 The :mod:`locale` module defines the following exception and functions:
26 Exception raised when :func:`setlocale` fails.
29 .. function:: setlocale(category[, locale])
31 If *locale* is specified, it may be a string, a tuple of the form ``(language
32 code, encoding)``, or ``None``. If it is a tuple, it is converted to a string
33 using the locale aliasing engine. If *locale* is given and not ``None``,
34 :func:`setlocale` modifies the locale setting for the *category*. The available
35 categories are listed in the data description below. The value is the name of a
36 locale. An empty string specifies the user's default settings. If the
37 modification of the locale fails, the exception :exc:`Error` is raised. If
38 successful, the new locale setting is returned.
40 If *locale* is omitted or ``None``, the current setting for *category* is
43 :func:`setlocale` is not thread safe on most systems. Applications typically
44 start with a call of ::
47 locale.setlocale(locale.LC_ALL, '')
49 This sets the locale for all categories to the user's default setting (typically
50 specified in the :envvar:`LANG` environment variable). If the locale is not
51 changed thereafter, using multithreading should not cause problems.
53 .. versionchanged:: 2.0
54 Added support for tuple values of the *locale* parameter.
57 .. function:: localeconv()
59 Returns the database of the local conventions as a dictionary. This dictionary
60 has the following strings as keys:
62 +----------------------+-------------------------------------+--------------------------------+
63 | Category | Key | Meaning |
64 +======================+=====================================+================================+
65 | :const:`LC_NUMERIC` | ``'decimal_point'`` | Decimal point character. |
66 +----------------------+-------------------------------------+--------------------------------+
67 | | ``'grouping'`` | Sequence of numbers specifying |
68 | | | which relative positions the |
69 | | | ``'thousands_sep'`` is |
70 | | | expected. If the sequence is |
71 | | | terminated with |
72 | | | :const:`CHAR_MAX`, no further |
73 | | | grouping is performed. If the |
74 | | | sequence terminates with a |
75 | | | ``0``, the last group size is |
76 | | | repeatedly used. |
77 +----------------------+-------------------------------------+--------------------------------+
78 | | ``'thousands_sep'`` | Character used between groups. |
79 +----------------------+-------------------------------------+--------------------------------+
80 | :const:`LC_MONETARY` | ``'int_curr_symbol'`` | International currency symbol. |
81 +----------------------+-------------------------------------+--------------------------------+
82 | | ``'currency_symbol'`` | Local currency symbol. |
83 +----------------------+-------------------------------------+--------------------------------+
84 | | ``'p_cs_precedes/n_cs_precedes'`` | Whether the currency symbol |
85 | | | precedes the value (for |
86 | | | positive resp. negative |
88 +----------------------+-------------------------------------+--------------------------------+
89 | | ``'p_sep_by_space/n_sep_by_space'`` | Whether the currency symbol is |
90 | | | separated from the value by a |
91 | | | space (for positive resp. |
92 | | | negative values). |
93 +----------------------+-------------------------------------+--------------------------------+
94 | | ``'mon_decimal_point'`` | Decimal point used for |
95 | | | monetary values. |
96 +----------------------+-------------------------------------+--------------------------------+
97 | | ``'frac_digits'`` | Number of fractional digits |
98 | | | used in local formatting of |
99 | | | monetary values. |
100 +----------------------+-------------------------------------+--------------------------------+
101 | | ``'int_frac_digits'`` | Number of fractional digits |
102 | | | used in international |
103 | | | formatting of monetary values. |
104 +----------------------+-------------------------------------+--------------------------------+
105 | | ``'mon_thousands_sep'`` | Group separator used for |
106 | | | monetary values. |
107 +----------------------+-------------------------------------+--------------------------------+
108 | | ``'mon_grouping'`` | Equivalent to ``'grouping'``, |
109 | | | used for monetary values. |
110 +----------------------+-------------------------------------+--------------------------------+
111 | | ``'positive_sign'`` | Symbol used to annotate a |
112 | | | positive monetary value. |
113 +----------------------+-------------------------------------+--------------------------------+
114 | | ``'negative_sign'`` | Symbol used to annotate a |
115 | | | negative monetary value. |
116 +----------------------+-------------------------------------+--------------------------------+
117 | | ``'p_sign_posn/n_sign_posn'`` | The position of the sign (for |
118 | | | positive resp. negative |
119 | | | values), see below. |
120 +----------------------+-------------------------------------+--------------------------------+
122 All numeric values can be set to :const:`CHAR_MAX` to indicate that there is no
123 value specified in this locale.
125 The possible values for ``'p_sign_posn'`` and ``'n_sign_posn'`` are given below.
127 +--------------+-----------------------------------------+
128 | Value | Explanation |
129 +==============+=========================================+
130 | ``0`` | Currency and value are surrounded by |
132 +--------------+-----------------------------------------+
133 | ``1`` | The sign should precede the value and |
134 | | currency symbol. |
135 +--------------+-----------------------------------------+
136 | ``2`` | The sign should follow the value and |
137 | | currency symbol. |
138 +--------------+-----------------------------------------+
139 | ``3`` | The sign should immediately precede the |
141 +--------------+-----------------------------------------+
142 | ``4`` | The sign should immediately follow the |
144 +--------------+-----------------------------------------+
145 | ``CHAR_MAX`` | Nothing is specified in this locale. |
146 +--------------+-----------------------------------------+
149 .. function:: nl_langinfo(option)
151 Return some locale-specific information as a string. This function is not
152 available on all systems, and the set of possible options might also vary across
153 platforms. The possible argument values are numbers, for which symbolic
154 constants are available in the locale module.
157 .. function:: getdefaultlocale([envvars])
159 Tries to determine the default locale settings and returns them as a tuple of
160 the form ``(language code, encoding)``.
162 According to POSIX, a program which has not called ``setlocale(LC_ALL, '')``
163 runs using the portable ``'C'`` locale. Calling ``setlocale(LC_ALL, '')`` lets
164 it use the default locale as defined by the :envvar:`LANG` variable. Since we
165 do not want to interfere with the current locale setting we thus emulate the
166 behavior in the way described above.
168 To maintain compatibility with other platforms, not only the :envvar:`LANG`
169 variable is tested, but a list of variables given as envvars parameter. The
170 first found to be defined will be used. *envvars* defaults to the search path
171 used in GNU gettext; it must always contain the variable name ``LANG``. The GNU
172 gettext search path contains ``'LANGUAGE'``, ``'LC_ALL'``, ``'LC_CTYPE'``, and
173 ``'LANG'``, in that order.
175 Except for the code ``'C'``, the language code corresponds to :rfc:`1766`.
176 *language code* and *encoding* may be ``None`` if their values cannot be
179 .. versionadded:: 2.0
182 .. function:: getlocale([category])
184 Returns the current setting for the given locale category as sequence containing
185 *language code*, *encoding*. *category* may be one of the :const:`LC_\*` values
186 except :const:`LC_ALL`. It defaults to :const:`LC_CTYPE`.
188 Except for the code ``'C'``, the language code corresponds to :rfc:`1766`.
189 *language code* and *encoding* may be ``None`` if their values cannot be
192 .. versionadded:: 2.0
195 .. function:: getpreferredencoding([do_setlocale])
197 Return the encoding used for text data, according to user preferences. User
198 preferences are expressed differently on different systems, and might not be
199 available programmatically on some systems, so this function only returns a
202 On some systems, it is necessary to invoke :func:`setlocale` to obtain the user
203 preferences, so this function is not thread-safe. If invoking setlocale is not
204 necessary or desired, *do_setlocale* should be set to ``False``.
206 .. versionadded:: 2.3
209 .. function:: normalize(localename)
211 Returns a normalized locale code for the given locale name. The returned locale
212 code is formatted for use with :func:`setlocale`. If normalization fails, the
213 original name is returned unchanged.
215 If the given encoding is not known, the function defaults to the default
216 encoding for the locale code just like :func:`setlocale`.
218 .. versionadded:: 2.0
221 .. function:: resetlocale([category])
223 Sets the locale for *category* to the default setting.
225 The default setting is determined by calling :func:`getdefaultlocale`.
226 *category* defaults to :const:`LC_ALL`.
228 .. versionadded:: 2.0
231 .. function:: strcoll(string1, string2)
233 Compares two strings according to the current :const:`LC_COLLATE` setting. As
234 any other compare function, returns a negative, or a positive value, or ``0``,
235 depending on whether *string1* collates before or after *string2* or is equal to
239 .. function:: strxfrm(string)
241 .. index:: builtin: cmp
243 Transforms a string to one that can be used for the built-in function
244 :func:`cmp`, and still returns locale-aware results. This function can be used
245 when the same string is compared repeatedly, e.g. when collating a sequence of
249 .. function:: format(format, val[, grouping[, monetary]])
251 Formats a number *val* according to the current :const:`LC_NUMERIC` setting.
252 The format follows the conventions of the ``%`` operator. For floating point
253 values, the decimal point is modified if appropriate. If *grouping* is true,
254 also takes the grouping into account.
256 If *monetary* is true, the conversion uses monetary thousands separator and
259 Please note that this function will only work for exactly one %char specifier.
260 For whole format strings, use :func:`format_string`.
262 .. versionchanged:: 2.5
263 Added the *monetary* parameter.
266 .. function:: format_string(format, val[, grouping])
268 Processes formatting specifiers as in ``format % val``, but takes the current
269 locale settings into account.
271 .. versionadded:: 2.5
274 .. function:: currency(val[, symbol[, grouping[, international]]])
276 Formats a number *val* according to the current :const:`LC_MONETARY` settings.
278 The returned string includes the currency symbol if *symbol* is true, which is
279 the default. If *grouping* is true (which is not the default), grouping is done
280 with the value. If *international* is true (which is not the default), the
281 international currency symbol is used.
283 Note that this function will not work with the 'C' locale, so you have to set a
284 locale via :func:`setlocale` first.
286 .. versionadded:: 2.5
289 .. function:: str(float)
291 Formats a floating point number using the same format as the built-in function
292 ``str(float)``, but takes the decimal point into account.
295 .. function:: atof(string)
297 Converts a string to a floating point number, following the :const:`LC_NUMERIC`
301 .. function:: atoi(string)
303 Converts a string to an integer, following the :const:`LC_NUMERIC` conventions.
308 .. index:: module: string
310 Locale category for the character type functions. Depending on the settings of
311 this category, the functions of module :mod:`string` dealing with case change
317 Locale category for sorting strings. The functions :func:`strcoll` and
318 :func:`strxfrm` of the :mod:`locale` module are affected.
323 Locale category for the formatting of time. The function :func:`time.strftime`
324 follows these conventions.
327 .. data:: LC_MONETARY
329 Locale category for formatting of monetary values. The available options are
330 available from the :func:`localeconv` function.
333 .. data:: LC_MESSAGES
335 Locale category for message display. Python currently does not support
336 application specific locale-aware messages. Messages displayed by the operating
337 system, like those returned by :func:`os.strerror` might be affected by this
343 Locale category for formatting numbers. The functions :func:`format`,
344 :func:`atoi`, :func:`atof` and :func:`str` of the :mod:`locale` module are
345 affected by that category. All other numeric formatting operations are not
351 Combination of all locale settings. If this flag is used when the locale is
352 changed, setting the locale for all categories is attempted. If that fails for
353 any category, no category is changed at all. When the locale is retrieved using
354 this flag, a string indicating the setting for all categories is returned. This
355 string can be later used to restore the settings.
360 This is a symbolic constant used for different values returned by
363 The :func:`nl_langinfo` function accepts one of the following keys. Most
364 descriptions are taken from the corresponding description in the GNU C library.
369 Return a string with the name of the character encoding used in the selected
375 Return a string that can be used as a format string for strftime(3) to represent
376 time and date in a locale-specific way.
381 Return a string that can be used as a format string for strftime(3) to represent
382 a date in a locale-specific way.
387 Return a string that can be used as a format string for strftime(3) to represent
388 a time in a locale-specific way.
393 The return value can be used as a format string for 'strftime' to represent time
397 .. data:: DAY_1 ... DAY_7
399 Return name of the n-th day of the week.
403 This follows the US convention of :const:`DAY_1` being Sunday, not the
404 international convention (ISO 8601) that Monday is the first day of the week.
407 .. data:: ABDAY_1 ... ABDAY_7
409 Return abbreviated name of the n-th day of the week.
412 .. data:: MON_1 ... MON_12
414 Return name of the n-th month.
417 .. data:: ABMON_1 ... ABMON_12
419 Return abbreviated name of the n-th month.
424 Return radix character (decimal dot, decimal comma, etc.)
429 Return separator character for thousands (groups of three digits).
434 Return a regular expression that can be used with the regex function to
435 recognize a positive response to a yes/no question.
439 The expression is in the syntax suitable for the :cfunc:`regex` function from
440 the C library, which might differ from the syntax used in :mod:`re`.
445 Return a regular expression that can be used with the regex(3) function to
446 recognize a negative response to a yes/no question.
451 Return the currency symbol, preceded by "-" if the symbol should appear before
452 the value, "+" if the symbol should appear after the value, or "." if the symbol
453 should replace the radix character.
458 The return value represents the era used in the current locale.
460 Most locales do not define this value. An example of a locale which does define
461 this value is the Japanese one. In Japan, the traditional representation of
462 dates includes the name of the era corresponding to the then-emperor's reign.
464 Normally it should not be necessary to use this value directly. Specifying the
465 ``E`` modifier in their format strings causes the :func:`strftime` function to
466 use this information. The format of the returned string is not specified, and
467 therefore you should not assume knowledge of it on different systems.
472 The return value gives the year in the relevant era of the locale.
475 .. data:: ERA_D_T_FMT
477 This return value can be used as a format string for :func:`strftime` to
478 represent dates and times in a locale-specific era-based way.
483 This return value can be used as a format string for :func:`strftime` to
484 represent time in a locale-specific era-based way.
489 The return value is a representation of up to 100 values used to represent the
495 >>> loc = locale.getlocale() # get current locale
496 >>> locale.setlocale(locale.LC_ALL, 'de_DE') # use German locale; name might vary with platform
497 >>> locale.strcoll('f\xe4n', 'foo') # compare a string containing an umlaut
498 >>> locale.setlocale(locale.LC_ALL, '') # use user's preferred locale
499 >>> locale.setlocale(locale.LC_ALL, 'C') # use default (C) locale
500 >>> locale.setlocale(locale.LC_ALL, loc) # restore saved locale
503 Background, details, hints, tips and caveats
504 --------------------------------------------
506 The C standard defines the locale as a program-wide property that may be
507 relatively expensive to change. On top of that, some implementation are broken
508 in such a way that frequent locale changes may cause core dumps. This makes the
509 locale somewhat painful to use correctly.
511 Initially, when a program is started, the locale is the ``C`` locale, no matter
512 what the user's preferred locale is. The program must explicitly say that it
513 wants the user's preferred locale settings by calling ``setlocale(LC_ALL, '')``.
515 It is generally a bad idea to call :func:`setlocale` in some library routine,
516 since as a side effect it affects the entire program. Saving and restoring it
517 is almost as bad: it is expensive and affects other threads that happen to run
518 before the settings have been restored.
520 If, when coding a module for general use, you need a locale independent version
521 of an operation that is affected by the locale (such as :func:`string.lower`, or
522 certain formats used with :func:`time.strftime`), you will have to find a way to
523 do it without using the standard library routine. Even better is convincing
524 yourself that using locale settings is okay. Only as a last resort should you
525 document that your module is not compatible with non-\ ``C`` locale settings.
527 .. index:: module: string
529 The case conversion functions in the :mod:`string` module are affected by the
530 locale settings. When a call to the :func:`setlocale` function changes the
531 :const:`LC_CTYPE` settings, the variables ``string.lowercase``,
532 ``string.uppercase`` and ``string.letters`` are recalculated. Note that code
533 that uses these variable through ':keyword:`from` ... :keyword:`import` ...',
534 e.g. ``from string import letters``, is not affected by subsequent
535 :func:`setlocale` calls.
537 The only way to perform numeric operations according to the locale is to use the
538 special functions defined by this module: :func:`atof`, :func:`atoi`,
539 :func:`format`, :func:`str`.
542 .. _embedding-locale:
544 For extension writers and programs that embed Python
545 ----------------------------------------------------
547 Extension modules should never call :func:`setlocale`, except to find out what
548 the current locale is. But since the return value can only be used portably to
549 restore it, that is not very useful (except perhaps to find out whether or not
550 the locale is ``C``).
552 When Python code uses the :mod:`locale` module to change the locale, this also
553 affects the embedding application. If the embedding application doesn't want
554 this to happen, it should remove the :mod:`_locale` extension module (which does
555 all the work) from the table of built-in modules in the :file:`config.c` file,
556 and make sure that the :mod:`_locale` module is not accessible as a shared
562 Access to message catalogs
563 --------------------------
565 The locale module exposes the C library's gettext interface on systems that
566 provide this interface. It consists of the functions :func:`gettext`,
567 :func:`dgettext`, :func:`dcgettext`, :func:`textdomain`, :func:`bindtextdomain`,
568 and :func:`bind_textdomain_codeset`. These are similar to the same functions in
569 the :mod:`gettext` module, but use the C library's binary format for message
570 catalogs, and the C library's search algorithms for locating message catalogs.
572 Python applications should normally find no need to invoke these functions, and
573 should use :mod:`gettext` instead. A known exception to this rule are
574 applications that link use additional C libraries which internally invoke
575 :cfunc:`gettext` or :func:`dcgettext`. For these applications, it may be
576 necessary to bind the text domain, so that the libraries can properly locate
577 their message catalogs.