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 +--------------+-----------------------------------------+ 149 150 151 .. 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 288 path used in GNU gettext; it must always contain the variable name 289 ``'LANG'``. The GNU gettext search path contains ``'LC_ALL'``, 290 ``'LC_CTYPE'``, ``'LANG'`` and ``'LANGUAGE'``, 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. 295 296 297 .. function:: getlocale(category=LC_CTYPE) 298 299 Returns the current setting for the given locale category as sequence containing 300 *language code*, *encoding*. *category* may be one of the :const:`LC_\*` values 301 except :const:`LC_ALL`. It defaults to :const:`LC_CTYPE`. 302 303 Except for the code ``'C'``, the language code corresponds to :rfc:`1766`. 304 *language code* and *encoding* may be ``None`` if their values cannot be 305 determined. 306 307 308 .. function:: getpreferredencoding(do_setlocale=True) 309 310 Return the encoding used for text data, according to user preferences. User 311 preferences are expressed differently on different systems, and might not be 312 available programmatically on some systems, so this function only returns a 313 guess. 314 315 On some systems, it is necessary to invoke :func:`setlocale` to obtain the user 316 preferences, so this function is not thread-safe. If invoking setlocale is not 317 necessary or desired, *do_setlocale* should be set to ``False``. 318 319 320 .. function:: normalize(localename) 321 322 Returns a normalized locale code for the given locale name. The returned locale 323 code is formatted for use with :func:`setlocale`. If normalization fails, the 324 original name is returned unchanged. 325 326 If the given encoding is not known, the function defaults to the default 327 encoding for the locale code just like :func:`setlocale`. 328 329 330 .. function:: resetlocale(category=LC_ALL) 331 332 Sets the locale for *category* to the default setting. 333 334 The default setting is determined by calling :func:`getdefaultlocale`. 335 *category* defaults to :const:`LC_ALL`. 336 337 338 .. function:: strcoll(string1, string2) 339 340 Compares two strings according to the current :const:`LC_COLLATE` setting. As 341 any other compare function, returns a negative, or a positive value, or ``0``, 342 depending on whether *string1* collates before or after *string2* or is equal to 343 it. 344 345 346 .. function:: strxfrm(string) 347 348 Transforms a string to one that can be used in locale-aware 349 comparisons. For example, ``strxfrm(s1) < strxfrm(s2)`` is 350 equivalent to ``strcoll(s1, s2) < 0``. This function can be used 351 when the same string is compared repeatedly, e.g. when collating a 352 sequence of strings. 353 354 355 .. function:: format(format, val, grouping=False, monetary=False) 356 357 Formats a number *val* according to the current :const:`LC_NUMERIC` setting. 358 The format follows the conventions of the ``%`` operator. For floating point 359 values, the decimal point is modified if appropriate. If *grouping* is true, 360 also takes the grouping into account. 361 362 If *monetary* is true, the conversion uses monetary thousands separator and 363 grouping strings. 364 365 Please note that this function will only work for exactly one %char specifier. 366 For whole format strings, use :func:`format_string`. 367 368 369 .. function:: format_string(format, val, grouping=False) 370 371 Processes formatting specifiers as in ``format % val``, but takes the current 372 locale settings into account. 373 374 375 .. function:: currency(val, symbol=True, grouping=False, international=False) 376 377 Formats a number *val* according to the current :const:`LC_MONETARY` settings. 378 379 The returned string includes the currency symbol if *symbol* is true, which is 380 the default. If *grouping* is true (which is not the default), grouping is done 381 with the value. If *international* is true (which is not the default), the 382 international currency symbol is used. 383 384 Note that this function will not work with the 'C' locale, so you have to set a 385 locale via :func:`setlocale` first. 386 387 388 .. function:: str(float) 389 390 Formats a floating point number using the same format as the built-in function 391 ``str(float)``, but takes the decimal point into account. 392 393 394 .. function:: delocalize(string) 395 396 Converts a string into a normalized number string, following the 397 :const:`LC_NUMERIC` settings. 398 399 .. versionadded:: 3.5 400 401 402 .. function:: atof(string) 403 404 Converts a string to a floating point number, following the :const:`LC_NUMERIC` 405 settings. 406 407 408 .. function:: atoi(string) 409 410 Converts a string to an integer, following the :const:`LC_NUMERIC` conventions. 411 412 413 .. data:: LC_CTYPE 414 415 .. index:: module: string 416 417 Locale category for the character type functions. Depending on the settings of 418 this category, the functions of module :mod:`string` dealing with case change 419 their behaviour. 420 421 422 .. data:: LC_COLLATE 423 424 Locale category for sorting strings. The functions :func:`strcoll` and 425 :func:`strxfrm` of the :mod:`locale` module are affected. 426 427 428 .. data:: LC_TIME 429 430 Locale category for the formatting of time. The function :func:`time.strftime` 431 follows these conventions. 432 433 434 .. data:: LC_MONETARY 435 436 Locale category for formatting of monetary values. The available options are 437 available from the :func:`localeconv` function. 438 439 440 .. data:: LC_MESSAGES 441 442 Locale category for message display. Python currently does not support 443 application specific locale-aware messages. Messages displayed by the operating 444 system, like those returned by :func:`os.strerror` might be affected by this 445 category. 446 447 448 .. data:: LC_NUMERIC 449 450 Locale category for formatting numbers. The functions :func:`.format`, 451 :func:`atoi`, :func:`atof` and :func:`.str` of the :mod:`locale` module are 452 affected by that category. All other numeric formatting operations are not 453 affected. 454 455 456 .. data:: LC_ALL 457 458 Combination of all locale settings. If this flag is used when the locale is 459 changed, setting the locale for all categories is attempted. If that fails for 460 any category, no category is changed at all. When the locale is retrieved using 461 this flag, a string indicating the setting for all categories is returned. This 462 string can be later used to restore the settings. 463 464 465 .. data:: CHAR_MAX 466 467 This is a symbolic constant used for different values returned by 468 :func:`localeconv`. 469 470 471 Example:: 472 473 >>> import locale 474 >>> loc = locale.getlocale() # get current locale 475 # use German locale; name might vary with platform 476 >>> locale.setlocale(locale.LC_ALL, 'de_DE') 477 >>> locale.strcoll('f\xe4n', 'foo') # compare a string containing an umlaut 478 >>> locale.setlocale(locale.LC_ALL, '') # use user's preferred locale 479 >>> locale.setlocale(locale.LC_ALL, 'C') # use default (C) locale 480 >>> locale.setlocale(locale.LC_ALL, loc) # restore saved locale 481 482 483 Background, details, hints, tips and caveats 484 -------------------------------------------- 485 486 The C standard defines the locale as a program-wide property that may be 487 relatively expensive to change. On top of that, some implementation are broken 488 in such a way that frequent locale changes may cause core dumps. This makes the 489 locale somewhat painful to use correctly. 490 491 Initially, when a program is started, the locale is the ``C`` locale, no matter 492 what the user's preferred locale is. There is one exception: the 493 :data:`LC_CTYPE` category is changed at startup to set the current locale 494 encoding to the user's preferred locale encoding. The program must explicitly 495 say that it wants the user's preferred locale settings for other categories by 496 calling ``setlocale(LC_ALL, '')``. 497 498 It is generally a bad idea to call :func:`setlocale` in some library routine, 499 since as a side effect it affects the entire program. Saving and restoring it 500 is almost as bad: it is expensive and affects other threads that happen to run 501 before the settings have been restored. 502 503 If, when coding a module for general use, you need a locale independent version 504 of an operation that is affected by the locale (such as 505 certain formats used with :func:`time.strftime`), you will have to find a way to 506 do it without using the standard library routine. Even better is convincing 507 yourself that using locale settings is okay. Only as a last resort should you 508 document that your module is not compatible with non-\ ``C`` locale settings. 509 510 The only way to perform numeric operations according to the locale is to use the 511 special functions defined by this module: :func:`atof`, :func:`atoi`, 512 :func:`.format`, :func:`.str`. 513 514 There is no way to perform case conversions and character classifications 515 according to the locale. For (Unicode) text strings these are done according 516 to the character value only, while for byte strings, the conversions and 517 classifications are done according to the ASCII value of the byte, and bytes 518 whose high bit is set (i.e., non-ASCII bytes) are never converted or considered 519 part of a character class such as letter or whitespace. 520 521 522 .. _embedding-locale: 523 524 For extension writers and programs that embed Python 525 ---------------------------------------------------- 526 527 Extension modules should never call :func:`setlocale`, except to find out what 528 the current locale is. But since the return value can only be used portably to 529 restore it, that is not very useful (except perhaps to find out whether or not 530 the locale is ``C``). 531 532 When Python code uses the :mod:`locale` module to change the locale, this also 533 affects the embedding application. If the embedding application doesn't want 534 this to happen, it should remove the :mod:`_locale` extension module (which does 535 all the work) from the table of built-in modules in the :file:`config.c` file, 536 and make sure that the :mod:`_locale` module is not accessible as a shared 537 library. 538 539 540 .. _locale-gettext: 541 542 Access to message catalogs 543 -------------------------- 544 545 The locale module exposes the C library's gettext interface on systems that 546 provide this interface. It consists of the functions :func:`gettext`, 547 :func:`dgettext`, :func:`dcgettext`, :func:`textdomain`, :func:`bindtextdomain`, 548 and :func:`bind_textdomain_codeset`. These are similar to the same functions in 549 the :mod:`gettext` module, but use the C library's binary format for message 550 catalogs, and the C library's search algorithms for locating message catalogs. 551 552 Python applications should normally find no need to invoke these functions, and 553 should use :mod:`gettext` instead. A known exception to this rule are 554 applications that link with additional C libraries which internally invoke 555 :c:func:`gettext` or :func:`dcgettext`. For these applications, it may be 556 necessary to bind the text domain, so that the libraries can properly locate 557 their message catalogs. 558 559
