1 2 :mod:`locale` --- Internationalization services 3 =============================================== 4 5 .. module:: locale 6 :synopsis: Internationalization services. 7 .. moduleauthor:: Martin von Lwis <martin (a] v.loewis.de> 8 .. sectionauthor:: Martin von Lwis <martin (a] v.loewis.de> 9 10 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. 15 16 .. index:: module: _locale 17 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. 20 21 The :mod:`locale` module defines the following exception and functions: 22 23 24 .. exception:: Error 25 26 Exception raised when the locale passed to :func:`setlocale` is not 27 recognized. 28 29 30 .. function:: setlocale(category[, locale]) 31 32 If *locale* is given and not ``None``, :func:`setlocale` modifies the locale 33 setting for the *category*. The available categories are listed in the data 34 description below. *locale* may be a string, or an iterable of two strings 35 (language code and encoding). If it's an iterable, it's converted to a locale 36 name using the locale aliasing engine. An empty string specifies the user's 37 default settings. If the modification of the locale fails, the exception 38 :exc:`Error` is raised. If successful, the new locale setting is returned. 39 40 If *locale* is omitted or ``None``, the current setting for *category* is 41 returned. 42 43 :func:`setlocale` is not thread-safe on most systems. Applications typically 44 start with a call of :: 45 46 import locale 47 locale.setlocale(locale.LC_ALL, '') 48 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. 52 53 .. versionchanged:: 2.0 54 Added support for iterable values of the *locale* parameter. 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 +--------------+-----------------------------------------+ 149 150 151 .. function:: nl_langinfo(option) 152 153 Return some locale-specific information as a string. This function is not 154 available on all systems, and the set of possible options might also vary 155 across platforms. The possible argument values are numbers, for which 156 symbolic constants are available in the locale module. 157 158 The :func:`nl_langinfo` function accepts one of the following keys. Most 159 descriptions are taken from the corresponding description in the GNU C 160 library. 161 162 .. data:: CODESET 163 164 Get a string with the name of the character encoding used in the 165 selected locale. 166 167 .. data:: D_T_FMT 168 169 Get a string that can be used as a format string for :func:`time.strftime` to 170 represent date and time in a locale-specific way. 171 172 .. data:: D_FMT 173 174 Get a string that can be used as a format string for :func:`time.strftime` to 175 represent a date in a locale-specific way. 176 177 .. data:: T_FMT 178 179 Get a string that can be used as a format string for :func:`time.strftime` to 180 represent a time in a locale-specific way. 181 182 .. data:: T_FMT_AMPM 183 184 Get a format string for :func:`time.strftime` to represent time in the am/pm 185 format. 186 187 .. data:: DAY_1 ... DAY_7 188 189 Get the name of the n-th day of the week. 190 191 .. note:: 192 193 This follows the US convention of :const:`DAY_1` being Sunday, not the 194 international convention (ISO 8601) that Monday is the first day of the 195 week. 196 197 .. data:: ABDAY_1 ... ABDAY_7 198 199 Get the abbreviated name of the n-th day of the week. 200 201 .. data:: MON_1 ... MON_12 202 203 Get the name of the n-th month. 204 205 .. data:: ABMON_1 ... ABMON_12 206 207 Get the abbreviated name of the n-th month. 208 209 .. data:: RADIXCHAR 210 211 Get the radix character (decimal dot, decimal comma, etc.). 212 213 .. data:: THOUSEP 214 215 Get the separator character for thousands (groups of three digits). 216 217 .. data:: YESEXPR 218 219 Get a regular expression that can be used with the regex function to 220 recognize a positive response to a yes/no question. 221 222 .. note:: 223 224 The expression is in the syntax suitable for the :c:func:`regex` function 225 from the C library, which might differ from the syntax used in :mod:`re`. 226 227 .. data:: NOEXPR 228 229 Get a regular expression that can be used with the regex(3) function to 230 recognize a negative response to a yes/no question. 231 232 .. data:: CRNCYSTR 233 234 Get the currency symbol, preceded by "-" if the symbol should appear before 235 the value, "+" if the symbol should appear after the value, or "." if the 236 symbol should replace the radix character. 237 238 .. data:: ERA 239 240 Get a string that represents the era used in the current locale. 241 242 Most locales do not define this value. An example of a locale which does 243 define this value is the Japanese one. In Japan, the traditional 244 representation of dates includes the name of the era corresponding to the 245 then-emperor's reign. 246 247 Normally it should not be necessary to use this value directly. Specifying 248 the ``E`` modifier in their format strings causes the :func:`time.strftime` 249 function to use this information. The format of the returned string is not 250 specified, and therefore you should not assume knowledge of it on different 251 systems. 252 253 .. data:: ERA_D_T_FMT 254 255 Get a format string for :func:`time.strftime` to represent date and time in a 256 locale-specific era-based way. 257 258 .. data:: ERA_D_FMT 259 260 Get a format string for :func:`time.strftime` to represent a date in a 261 locale-specific era-based way. 262 263 .. data:: ERA_T_FMT 264 265 Get a format string for :func:`time.strftime` to represent a time in a 266 locale-specific era-based way. 267 268 .. data:: ALT_DIGITS 269 270 Get a representation of up to 100 values used to represent the values 271 0 to 99. 272 273 274 .. function:: getdefaultlocale([envvars]) 275 276 Tries to determine the default locale settings and returns them as a tuple of 277 the form ``(language code, encoding)``. 278 279 According to POSIX, a program which has not called ``setlocale(LC_ALL, '')`` 280 runs using the portable ``'C'`` locale. Calling ``setlocale(LC_ALL, '')`` lets 281 it use the default locale as defined by the :envvar:`LANG` variable. Since we 282 do not want to interfere with the current locale setting we thus emulate the 283 behavior in the way described above. 284 285 To maintain compatibility with other platforms, not only the :envvar:`LANG` 286 variable is tested, but a list of variables given as envvars parameter. The 287 first found to be defined will be used. *envvars* defaults to the search path 288 used in GNU gettext; it must always contain the variable name ``LANG``. The GNU 289 gettext search path contains ``'LANGUAGE'``, ``'LC_ALL'``, ``'LC_CTYPE'``, and 290 ``'LANG'``, in that order. 291 292 Except for the code ``'C'``, the language code corresponds to :rfc:`1766`. 293 *language code* and *encoding* may be ``None`` if their values cannot be 294 determined. 295 296 .. versionadded:: 2.0 297 298 299 .. function:: getlocale([category]) 300 301 Returns the current setting for the given locale category as sequence containing 302 *language code*, *encoding*. *category* may be one of the :const:`LC_\*` values 303 except :const:`LC_ALL`. It defaults to :const:`LC_CTYPE`. 304 305 Except for the code ``'C'``, the language code corresponds to :rfc:`1766`. 306 *language code* and *encoding* may be ``None`` if their values cannot be 307 determined. 308 309 .. versionadded:: 2.0 310 311 312 .. function:: getpreferredencoding([do_setlocale]) 313 314 Return the encoding used for text data, according to user preferences. User 315 preferences are expressed differently on different systems, and might not be 316 available programmatically on some systems, so this function only returns a 317 guess. 318 319 On some systems, it is necessary to invoke :func:`setlocale` to obtain the user 320 preferences, so this function is not thread-safe. If invoking setlocale is not 321 necessary or desired, *do_setlocale* should be set to ``False``. 322 323 .. versionadded:: 2.3 324 325 326 .. function:: normalize(localename) 327 328 Returns a normalized locale code for the given locale name. The returned locale 329 code is formatted for use with :func:`setlocale`. If normalization fails, the 330 original name is returned unchanged. 331 332 If the given encoding is not known, the function defaults to the default 333 encoding for the locale code just like :func:`setlocale`. 334 335 .. versionadded:: 2.0 336 337 338 .. function:: resetlocale([category]) 339 340 Sets the locale for *category* to the default setting. 341 342 The default setting is determined by calling :func:`getdefaultlocale`. 343 *category* defaults to :const:`LC_ALL`. 344 345 .. versionadded:: 2.0 346 347 348 .. function:: strcoll(string1, string2) 349 350 Compares two strings according to the current :const:`LC_COLLATE` setting. As 351 any other compare function, returns a negative, or a positive value, or ``0``, 352 depending on whether *string1* collates before or after *string2* or is equal to 353 it. 354 355 356 .. function:: strxfrm(string) 357 358 .. index:: builtin: cmp 359 360 Transforms a string to one that can be used for the built-in function 361 :func:`cmp`, and still returns locale-aware results. This function can be used 362 when the same string is compared repeatedly, e.g. when collating a sequence of 363 strings. 364 365 366 .. function:: format(format, val[, grouping[, monetary]]) 367 368 Formats a number *val* according to the current :const:`LC_NUMERIC` setting. 369 The format follows the conventions of the ``%`` operator. For floating point 370 values, the decimal point is modified if appropriate. If *grouping* is true, 371 also takes the grouping into account. 372 373 If *monetary* is true, the conversion uses monetary thousands separator and 374 grouping strings. 375 376 Please note that this function will only work for exactly one %char specifier. 377 For whole format strings, use :func:`format_string`. 378 379 .. versionchanged:: 2.5 380 Added the *monetary* parameter. 381 382 383 .. function:: format_string(format, val[, grouping]) 384 385 Processes formatting specifiers as in ``format % val``, but takes the current 386 locale settings into account. 387 388 .. versionadded:: 2.5 389 390 391 .. function:: currency(val[, symbol[, grouping[, international]]]) 392 393 Formats a number *val* according to the current :const:`LC_MONETARY` settings. 394 395 The returned string includes the currency symbol if *symbol* is true, which is 396 the default. If *grouping* is true (which is not the default), grouping is done 397 with the value. If *international* is true (which is not the default), the 398 international currency symbol is used. 399 400 Note that this function will not work with the 'C' locale, so you have to set a 401 locale via :func:`setlocale` first. 402 403 .. versionadded:: 2.5 404 405 406 .. function:: str(float) 407 408 Formats a floating point number using the same format as the built-in function 409 ``str(float)``, but takes the decimal point into account. 410 411 412 .. function:: atof(string) 413 414 Converts a string to a floating point number, following the :const:`LC_NUMERIC` 415 settings. 416 417 418 .. function:: atoi(string) 419 420 Converts a string to an integer, following the :const:`LC_NUMERIC` conventions. 421 422 423 .. data:: LC_CTYPE 424 425 .. index:: module: string 426 427 Locale category for the character type functions. Depending on the settings of 428 this category, the functions of module :mod:`string` dealing with case change 429 their behaviour. 430 431 432 .. data:: LC_COLLATE 433 434 Locale category for sorting strings. The functions :func:`strcoll` and 435 :func:`strxfrm` of the :mod:`locale` module are affected. 436 437 438 .. data:: LC_TIME 439 440 Locale category for the formatting of time. The function :func:`time.strftime` 441 follows these conventions. 442 443 444 .. data:: LC_MONETARY 445 446 Locale category for formatting of monetary values. The available options are 447 available from the :func:`localeconv` function. 448 449 450 .. data:: LC_MESSAGES 451 452 Locale category for message display. Python currently does not support 453 application specific locale-aware messages. Messages displayed by the operating 454 system, like those returned by :func:`os.strerror` might be affected by this 455 category. 456 457 458 .. data:: LC_NUMERIC 459 460 Locale category for formatting numbers. The functions :func:`.format`, 461 :func:`atoi`, :func:`atof` and :func:`.str` of the :mod:`locale` module are 462 affected by that category. All other numeric formatting operations are not 463 affected. 464 465 466 .. data:: LC_ALL 467 468 Combination of all locale settings. If this flag is used when the locale is 469 changed, setting the locale for all categories is attempted. If that fails for 470 any category, no category is changed at all. When the locale is retrieved using 471 this flag, a string indicating the setting for all categories is returned. This 472 string can be later used to restore the settings. 473 474 475 .. data:: CHAR_MAX 476 477 This is a symbolic constant used for different values returned by 478 :func:`localeconv`. 479 480 481 Example:: 482 483 >>> import locale 484 >>> loc = locale.getlocale() # get current locale 485 # use German locale; name might vary with platform 486 >>> locale.setlocale(locale.LC_ALL, 'de_DE') 487 >>> locale.strcoll('f\xe4n', 'foo') # compare a string containing an umlaut 488 >>> locale.setlocale(locale.LC_ALL, '') # use user's preferred locale 489 >>> locale.setlocale(locale.LC_ALL, 'C') # use default (C) locale 490 >>> locale.setlocale(locale.LC_ALL, loc) # restore saved locale 491 492 493 Background, details, hints, tips and caveats 494 -------------------------------------------- 495 496 The C standard defines the locale as a program-wide property that may be 497 relatively expensive to change. On top of that, some implementation are broken 498 in such a way that frequent locale changes may cause core dumps. This makes the 499 locale somewhat painful to use correctly. 500 501 Initially, when a program is started, the locale is the ``C`` locale, no matter 502 what the user's preferred locale is. The program must explicitly say that it 503 wants the user's preferred locale settings by calling ``setlocale(LC_ALL, '')``. 504 505 It is generally a bad idea to call :func:`setlocale` in some library routine, 506 since as a side effect it affects the entire program. Saving and restoring it 507 is almost as bad: it is expensive and affects other threads that happen to run 508 before the settings have been restored. 509 510 If, when coding a module for general use, you need a locale independent version 511 of an operation that is affected by the locale (such as :func:`string.lower`, or 512 certain formats used with :func:`time.strftime`), you will have to find a way to 513 do it without using the standard library routine. Even better is convincing 514 yourself that using locale settings is okay. Only as a last resort should you 515 document that your module is not compatible with non-\ ``C`` locale settings. 516 517 .. index:: module: string 518 519 The case conversion functions in the :mod:`string` module are affected by the 520 locale settings. When a call to the :func:`setlocale` function changes the 521 :const:`LC_CTYPE` settings, the variables ``string.lowercase``, 522 ``string.uppercase`` and ``string.letters`` are recalculated. Note that code 523 that uses these variable through ':keyword:`from` ... :keyword:`import` ...', 524 e.g. ``from string import letters``, is not affected by subsequent 525 :func:`setlocale` calls. 526 527 The only way to perform numeric operations according to the locale is to use the 528 special functions defined by this module: :func:`atof`, :func:`atoi`, 529 :func:`.format`, :func:`.str`. 530 531 532 .. _embedding-locale: 533 534 For extension writers and programs that embed Python 535 ---------------------------------------------------- 536 537 Extension modules should never call :func:`setlocale`, except to find out what 538 the current locale is. But since the return value can only be used portably to 539 restore it, that is not very useful (except perhaps to find out whether or not 540 the locale is ``C``). 541 542 When Python code uses the :mod:`locale` module to change the locale, this also 543 affects the embedding application. If the embedding application doesn't want 544 this to happen, it should remove the :mod:`_locale` extension module (which does 545 all the work) from the table of built-in modules in the :file:`config.c` file, 546 and make sure that the :mod:`_locale` module is not accessible as a shared 547 library. 548 549 550 .. _locale-gettext: 551 552 Access to message catalogs 553 -------------------------- 554 555 The locale module exposes the C library's gettext interface on systems that 556 provide this interface. It consists of the functions :func:`gettext`, 557 :func:`dgettext`, :func:`dcgettext`, :func:`textdomain`, :func:`bindtextdomain`, 558 and :func:`bind_textdomain_codeset`. These are similar to the same functions in 559 the :mod:`gettext` module, but use the C library's binary format for message 560 catalogs, and the C library's search algorithms for locating message catalogs. 561 562 Python applications should normally find no need to invoke these functions, and 563 should use :mod:`gettext` instead. A known exception to this rule are 564 applications that link with additional C libraries which internally invoke 565 :c:func:`gettext` or :func:`dcgettext`. For these applications, it may be 566 necessary to bind the text domain, so that the libraries can properly locate 567 their message catalogs. 568 569
