1 :mod:`locale` --- Internationalization services 2 =============================================== 3 4 .. module:: locale 5 :synopsis: Internationalization services. 6 7 .. moduleauthor:: Martin von Lwis <martin (a] v.loewis.de> 8 .. sectionauthor:: Martin von Lwis <martin (a] v.loewis.de> 9 10 **Source code:** :source:`Lib/locale.py` 11 12 -------------- 13 14 The :mod:`locale` module opens access to the POSIX locale database and 15 functionality. The POSIX locale mechanism allows programmers to deal with 16 certain cultural issues in an application, without requiring the programmer to 17 know all the specifics of each country where the software is executed. 18 19 .. index:: module: _locale 20 21 The :mod:`locale` module is implemented on top of the :mod:`_locale` module, 22 which in turn uses an ANSI C locale implementation if available. 23 24 The :mod:`locale` module defines the following exception and functions: 25 26 27 .. exception:: Error 28 29 Exception raised when the locale passed to :func:`setlocale` is not 30 recognized. 31 32 33 .. function:: setlocale(category, locale=None) 34 35 If *locale* is given and not ``None``, :func:`setlocale` modifies the locale 36 setting for the *category*. The available categories are listed in the data 37 description below. *locale* may be a string, or an iterable of two strings 38 (language code and encoding). If it's an iterable, it's converted to a locale 39 name using the locale aliasing engine. An empty string specifies the user's 40 default settings. If the modification of the locale fails, the exception 41 :exc:`Error` is raised. If successful, the new locale setting is returned. 42 43 If *locale* is omitted or ``None``, the current setting for *category* is 44 returned. 45 46 :func:`setlocale` is not thread-safe on most systems. Applications typically 47 start with a call of :: 48 49 import locale 50 locale.setlocale(locale.LC_ALL, '') 51 52 This sets the locale for all categories to the user's default setting (typically 53 specified in the :envvar:`LANG` environment variable). If the locale is not 54 changed thereafter, using multithreading should not cause problems. 55 56 57 .. function:: localeconv() 58 59 Returns the database of the local conventions as a dictionary. This dictionary 60 has the following strings as keys: 61 62 .. tabularcolumns:: |l|l|L| 63 64 +----------------------+-------------------------------------+--------------------------------+ 65 | Category | Key | Meaning | 66 +======================+=====================================+================================+ 67 | :const:`LC_NUMERIC` | ``'decimal_point'`` | Decimal point character. | 68 +----------------------+-------------------------------------+--------------------------------+ 69 | | ``'grouping'`` | Sequence of numbers specifying | 70 | | | which relative positions the | 71 | | | ``'thousands_sep'`` is | 72 | | | expected. If the sequence is | 73 | | | terminated with | 74 | | | :const:`CHAR_MAX`, no further | 75 | | | grouping is performed. If the | 76 | | | sequence terminates with a | 77 | | | ``0``, the last group size is | 78 | | | repeatedly used. | 79 +----------------------+-------------------------------------+--------------------------------+ 80 | | ``'thousands_sep'`` | Character used between groups. | 81 +----------------------+-------------------------------------+--------------------------------+ 82 | :const:`LC_MONETARY` | ``'int_curr_symbol'`` | International currency symbol. | 83 +----------------------+-------------------------------------+--------------------------------+ 84 | | ``'currency_symbol'`` | Local currency symbol. | 85 +----------------------+-------------------------------------+--------------------------------+ 86 | | ``'p_cs_precedes/n_cs_precedes'`` | Whether the currency symbol | 87 | | | precedes the value (for | 88 | | | positive resp. negative | 89 | | | values). | 90 +----------------------+-------------------------------------+--------------------------------+ 91 | | ``'p_sep_by_space/n_sep_by_space'`` | Whether the currency symbol is | 92 | | | separated from the value by a | 93 | | | space (for positive resp. | 94 | | | negative values). | 95 +----------------------+-------------------------------------+--------------------------------+ 96 | | ``'mon_decimal_point'`` | Decimal point used for | 97 | | | monetary values. | 98 +----------------------+-------------------------------------+--------------------------------+ 99 | | ``'frac_digits'`` | Number of fractional digits | 100 | | | used in local formatting of | 101 | | | monetary values. | 102 +----------------------+-------------------------------------+--------------------------------+ 103 | | ``'int_frac_digits'`` | Number of fractional digits | 104 | | | used in international | 105 | | | formatting of monetary values. | 106 +----------------------+-------------------------------------+--------------------------------+ 107 | | ``'mon_thousands_sep'`` | Group separator used for | 108 | | | monetary values. | 109 +----------------------+-------------------------------------+--------------------------------+ 110 | | ``'mon_grouping'`` | Equivalent to ``'grouping'``, | 111 | | | used for monetary values. | 112 +----------------------+-------------------------------------+--------------------------------+ 113 | | ``'positive_sign'`` | Symbol used to annotate a | 114 | | | positive monetary value. | 115 +----------------------+-------------------------------------+--------------------------------+ 116 | | ``'negative_sign'`` | Symbol used to annotate a | 117 | | | negative monetary value. | 118 +----------------------+-------------------------------------+--------------------------------+ 119 | | ``'p_sign_posn/n_sign_posn'`` | The position of the sign (for | 120 | | | positive resp. negative | 121 | | | values), see below. | 122 +----------------------+-------------------------------------+--------------------------------+ 123 124 All numeric values can be set to :const:`CHAR_MAX` to indicate that there is no 125 value specified in this locale. 126 127 The possible values for ``'p_sign_posn'`` and ``'n_sign_posn'`` are given below. 128 129 +--------------+-----------------------------------------+ 130 | Value | Explanation | 131 +==============+=========================================+ 132 | ``0`` | Currency and value are surrounded by | 133 | | parentheses. | 134 +--------------+-----------------------------------------+ 135 | ``1`` | The sign should precede the value and | 136 | | currency symbol. | 137 +--------------+-----------------------------------------+ 138 | ``2`` | The sign should follow the value and | 139 | | currency symbol. | 140 +--------------+-----------------------------------------+ 141 | ``3`` | The sign should immediately precede the | 142 | | value. | 143 +--------------+-----------------------------------------+ 144 | ``4`` | The sign should immediately follow the | 145 | | value. | 146 +--------------+-----------------------------------------+ 147 | ``CHAR_MAX`` | Nothing is specified in this locale. | 148 +--------------+-----------------------------------------+ 149 150 The function sets temporarily the ``LC_CTYPE`` locale to the ``LC_NUMERIC`` 151 locale or the ``LC_MONETARY`` locale if locales are different and numeric or 152 monetary strings are non-ASCII. This temporary change affects other threads. 153 154 .. versionchanged:: 3.7 155 The function now sets temporarily the ``LC_CTYPE`` locale to the 156 ``LC_NUMERIC`` locale in some cases. 157 158 159 .. function:: nl_langinfo(option) 160 161 Return some locale-specific information as a string. This function is not 162 available on all systems, and the set of possible options might also vary 163 across platforms. The possible argument values are numbers, for which 164 symbolic constants are available in the locale module. 165 166 The :func:`nl_langinfo` function accepts one of the following keys. Most 167 descriptions are taken from the corresponding description in the GNU C 168 library. 169 170 .. data:: CODESET 171 172 Get a string with the name of the character encoding used in the 173 selected locale. 174 175 .. data:: D_T_FMT 176 177 Get a string that can be used as a format string for :func:`time.strftime` to 178 represent date and time in a locale-specific way. 179 180 .. data:: D_FMT 181 182 Get a string that can be used as a format string for :func:`time.strftime` to 183 represent a date in a locale-specific way. 184 185 .. data:: T_FMT 186 187 Get a string that can be used as a format string for :func:`time.strftime` to 188 represent a time in a locale-specific way. 189 190 .. data:: T_FMT_AMPM 191 192 Get a format string for :func:`time.strftime` to represent time in the am/pm 193 format. 194 195 .. data:: DAY_1 ... DAY_7 196 197 Get the name of the n-th day of the week. 198 199 .. note:: 200 201 This follows the US convention of :const:`DAY_1` being Sunday, not the 202 international convention (ISO 8601) that Monday is the first day of the 203 week. 204 205 .. data:: ABDAY_1 ... ABDAY_7 206 207 Get the abbreviated name of the n-th day of the week. 208 209 .. data:: MON_1 ... MON_12 210 211 Get the name of the n-th month. 212 213 .. data:: ABMON_1 ... ABMON_12 214 215 Get the abbreviated name of the n-th month. 216 217 .. data:: RADIXCHAR 218 219 Get the radix character (decimal dot, decimal comma, etc.). 220 221 .. data:: THOUSEP 222 223 Get the separator character for thousands (groups of three digits). 224 225 .. data:: YESEXPR 226 227 Get a regular expression that can be used with the regex function to 228 recognize a positive response to a yes/no question. 229 230 .. note:: 231 232 The expression is in the syntax suitable for the :c:func:`regex` function 233 from the C library, which might differ from the syntax used in :mod:`re`. 234 235 .. data:: NOEXPR 236 237 Get a regular expression that can be used with the regex(3) function to 238 recognize a negative response to a yes/no question. 239 240 .. data:: CRNCYSTR 241 242 Get the currency symbol, preceded by "-" if the symbol should appear before 243 the value, "+" if the symbol should appear after the value, or "." if the 244 symbol should replace the radix character. 245 246 .. data:: ERA 247 248 Get a string that represents the era used in the current locale. 249 250 Most locales do not define this value. An example of a locale which does 251 define this value is the Japanese one. In Japan, the traditional 252 representation of dates includes the name of the era corresponding to the 253 then-emperor's reign. 254 255 Normally it should not be necessary to use this value directly. Specifying 256 the ``E`` modifier in their format strings causes the :func:`time.strftime` 257 function to use this information. The format of the returned string is not 258 specified, and therefore you should not assume knowledge of it on different 259 systems. 260 261 .. data:: ERA_D_T_FMT 262 263 Get a format string for :func:`time.strftime` to represent date and time in a 264 locale-specific era-based way. 265 266 .. data:: ERA_D_FMT 267 268 Get a format string for :func:`time.strftime` to represent a date in a 269 locale-specific era-based way. 270 271 .. data:: ERA_T_FMT 272 273 Get a format string for :func:`time.strftime` to represent a time in a 274 locale-specific era-based way. 275 276 .. data:: ALT_DIGITS 277 278 Get a representation of up to 100 values used to represent the values 279 0 to 99. 280 281 282 .. function:: getdefaultlocale([envvars]) 283 284 Tries to determine the default locale settings and returns them as a tuple of 285 the form ``(language code, encoding)``. 286 287 According to POSIX, a program which has not called ``setlocale(LC_ALL, '')`` 288 runs using the portable ``'C'`` locale. Calling ``setlocale(LC_ALL, '')`` lets 289 it use the default locale as defined by the :envvar:`LANG` variable. Since we 290 do not want to interfere with the current locale setting we thus emulate the 291 behavior in the way described above. 292 293 To maintain compatibility with other platforms, not only the :envvar:`LANG` 294 variable is tested, but a list of variables given as envvars parameter. The 295 first found to be defined will be used. *envvars* defaults to the search 296 path used in GNU gettext; it must always contain the variable name 297 ``'LANG'``. The GNU gettext search path contains ``'LC_ALL'``, 298 ``'LC_CTYPE'``, ``'LANG'`` and ``'LANGUAGE'``, in that order. 299 300 Except for the code ``'C'``, the language code corresponds to :rfc:`1766`. 301 *language code* and *encoding* may be ``None`` if their values cannot be 302 determined. 303 304 305 .. function:: getlocale(category=LC_CTYPE) 306 307 Returns the current setting for the given locale category as sequence containing 308 *language code*, *encoding*. *category* may be one of the :const:`LC_\*` values 309 except :const:`LC_ALL`. It defaults to :const:`LC_CTYPE`. 310 311 Except for the code ``'C'``, the language code corresponds to :rfc:`1766`. 312 *language code* and *encoding* may be ``None`` if their values cannot be 313 determined. 314 315 316 .. function:: getpreferredencoding(do_setlocale=True) 317 318 Return the encoding used for text data, according to user preferences. User 319 preferences are expressed differently on different systems, and might not be 320 available programmatically on some systems, so this function only returns a 321 guess. 322 323 On some systems, it is necessary to invoke :func:`setlocale` to obtain the user 324 preferences, so this function is not thread-safe. If invoking setlocale is not 325 necessary or desired, *do_setlocale* should be set to ``False``. 326 327 On Android or in the UTF-8 mode (:option:`-X` ``utf8`` option), always 328 return ``'UTF-8'``, the locale and the *do_setlocale* argument are ignored. 329 330 .. versionchanged:: 3.7 331 The function now always returns ``UTF-8`` on Android or if the UTF-8 mode 332 is enabled. 333 334 335 .. function:: normalize(localename) 336 337 Returns a normalized locale code for the given locale name. The returned locale 338 code is formatted for use with :func:`setlocale`. If normalization fails, the 339 original name is returned unchanged. 340 341 If the given encoding is not known, the function defaults to the default 342 encoding for the locale code just like :func:`setlocale`. 343 344 345 .. function:: resetlocale(category=LC_ALL) 346 347 Sets the locale for *category* to the default setting. 348 349 The default setting is determined by calling :func:`getdefaultlocale`. 350 *category* defaults to :const:`LC_ALL`. 351 352 353 .. function:: strcoll(string1, string2) 354 355 Compares two strings according to the current :const:`LC_COLLATE` setting. As 356 any other compare function, returns a negative, or a positive value, or ``0``, 357 depending on whether *string1* collates before or after *string2* or is equal to 358 it. 359 360 361 .. function:: strxfrm(string) 362 363 Transforms a string to one that can be used in locale-aware 364 comparisons. For example, ``strxfrm(s1) < strxfrm(s2)`` is 365 equivalent to ``strcoll(s1, s2) < 0``. This function can be used 366 when the same string is compared repeatedly, e.g. when collating a 367 sequence of strings. 368 369 370 .. function:: format_string(format, val, grouping=False, monetary=False) 371 372 Formats a number *val* according to the current :const:`LC_NUMERIC` setting. 373 The format follows the conventions of the ``%`` operator. For floating point 374 values, the decimal point is modified if appropriate. If *grouping* is true, 375 also takes the grouping into account. 376 377 If *monetary* is true, the conversion uses monetary thousands separator and 378 grouping strings. 379 380 Processes formatting specifiers as in ``format % val``, but takes the current 381 locale settings into account. 382 383 .. versionchanged:: 3.7 384 The *monetary* keyword parameter was added. 385 386 387 .. function:: format(format, val, grouping=False, monetary=False) 388 389 Please note that this function works like :meth:`format_string` but will 390 only work for exactly one ``%char`` specifier. For example, ``'%f'`` and 391 ``'%.0f'`` are both valid specifiers, but ``'%f KiB'`` is not. 392 393 For whole format strings, use :func:`format_string`. 394 395 .. deprecated:: 3.7 396 Use :meth:`format_string` instead. 397 398 399 .. function:: currency(val, symbol=True, grouping=False, international=False) 400 401 Formats a number *val* according to the current :const:`LC_MONETARY` settings. 402 403 The returned string includes the currency symbol if *symbol* is true, which is 404 the default. If *grouping* is true (which is not the default), grouping is done 405 with the value. If *international* is true (which is not the default), the 406 international currency symbol is used. 407 408 Note that this function will not work with the 'C' locale, so you have to set a 409 locale via :func:`setlocale` first. 410 411 412 .. function:: str(float) 413 414 Formats a floating point number using the same format as the built-in function 415 ``str(float)``, but takes the decimal point into account. 416 417 418 .. function:: delocalize(string) 419 420 Converts a string into a normalized number string, following the 421 :const:`LC_NUMERIC` settings. 422 423 .. versionadded:: 3.5 424 425 426 .. function:: atof(string) 427 428 Converts a string to a floating point number, following the :const:`LC_NUMERIC` 429 settings. 430 431 432 .. function:: atoi(string) 433 434 Converts a string to an integer, following the :const:`LC_NUMERIC` conventions. 435 436 437 .. data:: LC_CTYPE 438 439 .. index:: module: string 440 441 Locale category for the character type functions. Depending on the settings of 442 this category, the functions of module :mod:`string` dealing with case change 443 their behaviour. 444 445 446 .. data:: LC_COLLATE 447 448 Locale category for sorting strings. The functions :func:`strcoll` and 449 :func:`strxfrm` of the :mod:`locale` module are affected. 450 451 452 .. data:: LC_TIME 453 454 Locale category for the formatting of time. The function :func:`time.strftime` 455 follows these conventions. 456 457 458 .. data:: LC_MONETARY 459 460 Locale category for formatting of monetary values. The available options are 461 available from the :func:`localeconv` function. 462 463 464 .. data:: LC_MESSAGES 465 466 Locale category for message display. Python currently does not support 467 application specific locale-aware messages. Messages displayed by the operating 468 system, like those returned by :func:`os.strerror` might be affected by this 469 category. 470 471 472 .. data:: LC_NUMERIC 473 474 Locale category for formatting numbers. The functions :func:`.format`, 475 :func:`atoi`, :func:`atof` and :func:`.str` of the :mod:`locale` module are 476 affected by that category. All other numeric formatting operations are not 477 affected. 478 479 480 .. data:: LC_ALL 481 482 Combination of all locale settings. If this flag is used when the locale is 483 changed, setting the locale for all categories is attempted. If that fails for 484 any category, no category is changed at all. When the locale is retrieved using 485 this flag, a string indicating the setting for all categories is returned. This 486 string can be later used to restore the settings. 487 488 489 .. data:: CHAR_MAX 490 491 This is a symbolic constant used for different values returned by 492 :func:`localeconv`. 493 494 495 Example:: 496 497 >>> import locale 498 >>> loc = locale.getlocale() # get current locale 499 # use German locale; name might vary with platform 500 >>> locale.setlocale(locale.LC_ALL, 'de_DE') 501 >>> locale.strcoll('f\xe4n', 'foo') # compare a string containing an umlaut 502 >>> locale.setlocale(locale.LC_ALL, '') # use user's preferred locale 503 >>> locale.setlocale(locale.LC_ALL, 'C') # use default (C) locale 504 >>> locale.setlocale(locale.LC_ALL, loc) # restore saved locale 505 506 507 Background, details, hints, tips and caveats 508 -------------------------------------------- 509 510 The C standard defines the locale as a program-wide property that may be 511 relatively expensive to change. On top of that, some implementation are broken 512 in such a way that frequent locale changes may cause core dumps. This makes the 513 locale somewhat painful to use correctly. 514 515 Initially, when a program is started, the locale is the ``C`` locale, no matter 516 what the user's preferred locale is. There is one exception: the 517 :data:`LC_CTYPE` category is changed at startup to set the current locale 518 encoding to the user's preferred locale encoding. The program must explicitly 519 say that it wants the user's preferred locale settings for other categories by 520 calling ``setlocale(LC_ALL, '')``. 521 522 It is generally a bad idea to call :func:`setlocale` in some library routine, 523 since as a side effect it affects the entire program. Saving and restoring it 524 is almost as bad: it is expensive and affects other threads that happen to run 525 before the settings have been restored. 526 527 If, when coding a module for general use, you need a locale independent version 528 of an operation that is affected by the locale (such as 529 certain formats used with :func:`time.strftime`), you will have to find a way to 530 do it without using the standard library routine. Even better is convincing 531 yourself that using locale settings is okay. Only as a last resort should you 532 document that your module is not compatible with non-\ ``C`` locale settings. 533 534 The only way to perform numeric operations according to the locale is to use the 535 special functions defined by this module: :func:`atof`, :func:`atoi`, 536 :func:`.format`, :func:`.str`. 537 538 There is no way to perform case conversions and character classifications 539 according to the locale. For (Unicode) text strings these are done according 540 to the character value only, while for byte strings, the conversions and 541 classifications are done according to the ASCII value of the byte, and bytes 542 whose high bit is set (i.e., non-ASCII bytes) are never converted or considered 543 part of a character class such as letter or whitespace. 544 545 546 .. _embedding-locale: 547 548 For extension writers and programs that embed Python 549 ---------------------------------------------------- 550 551 Extension modules should never call :func:`setlocale`, except to find out what 552 the current locale is. But since the return value can only be used portably to 553 restore it, that is not very useful (except perhaps to find out whether or not 554 the locale is ``C``). 555 556 When Python code uses the :mod:`locale` module to change the locale, this also 557 affects the embedding application. If the embedding application doesn't want 558 this to happen, it should remove the :mod:`_locale` extension module (which does 559 all the work) from the table of built-in modules in the :file:`config.c` file, 560 and make sure that the :mod:`_locale` module is not accessible as a shared 561 library. 562 563 564 .. _locale-gettext: 565 566 Access to message catalogs 567 -------------------------- 568 569 .. function:: gettext(msg) 570 .. function:: dgettext(domain, msg) 571 .. function:: dcgettext(domain, msg, category) 572 .. function:: textdomain(domain) 573 .. function:: bindtextdomain(domain, dir) 574 575 The locale module exposes the C library's gettext interface on systems that 576 provide this interface. It consists of the functions :func:`!gettext`, 577 :func:`!dgettext`, :func:`!dcgettext`, :func:`!textdomain`, :func:`!bindtextdomain`, 578 and :func:`!bind_textdomain_codeset`. These are similar to the same functions in 579 the :mod:`gettext` module, but use the C library's binary format for message 580 catalogs, and the C library's search algorithms for locating message catalogs. 581 582 Python applications should normally find no need to invoke these functions, and 583 should use :mod:`gettext` instead. A known exception to this rule are 584 applications that link with additional C libraries which internally invoke 585 :c:func:`gettext` or :c:func:`dcgettext`. For these applications, it may be 586 necessary to bind the text domain, so that the libraries can properly locate 587 their message catalogs. 588 589
