6.27 locale -- Internationalization services

Python PEP

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6.27 `locale` -- Internationalization services

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 Error: Exception raised when setlocale() fails.

setlocale( category[, locale])

If locale is specified, it may be a string, a tuple of the form (language code, encoding), or None. If it is a tuple, it is converted to a string using the locale aliasing engine. 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. The value is the name of a locale. 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 omitted or None, the current setting for category is returned.

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.

Changed in version 2.0: Added support for tuple values of the locale parameter.

localeconv( )

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

Key	Category	Meaning
`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.
	`'mon_decimal_point'`	Decimal point used for 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.
	`'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.

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.
`LC_MAX`	Nothing is specified in this 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.

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 'LANGUAGE', 'LC_ALL', 'LC_CTYPE', and 'LANG', in that order.

Except for the code 'C', the language code corresponds to RFC 1766. language code and encoding may be None if their values cannot be determined. New in version 2.0.

getlocale( [category]): Returns the current setting for the given locale category as sequence containing language code, encoding. category may be one of the LC_* values except LC_ALL. It defaults to LC_CTYPE.
Except for the code 'C', the language code corresponds to RFC 1766. language code and encoding may be None if their values cannot be determined. New in version 2.0.

getpreferredencoding( [do_setlocale])

Return the 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.

New in version 2.3.

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(). New in version 2.0.

resetlocale( [category]): Sets the locale for category to the default setting.
The default setting is determined by calling getdefaultlocale(). category defaults to LC_ALL. New in version 2.0.

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.

strxfrm( string): Transforms a string to one that can be used for the built-in function cmp(), and still returns locale-aware results. This function can be used when the same string is compared repeatedly, e.g. when collating a sequence of strings.

format( format, val[, grouping]): 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.

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.

atof( string): Converts a string to a floating point number, following the LC_NUMERIC settings.

atoi( string): Converts a string to an integer, following the LC_NUMERIC conventions.

LC_CTYPE: Locale category for the character type functions. Depending on the settings of this category, the functions of module string dealing with case change their behaviour.

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

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

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

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.

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

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.

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

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

CODESET: Return a string with the name of the character encoding used in the selected locale.

D_T_FMT: Return a string that can be used as a format string for strftime(3) to represent time and date in a locale-specific way.

D_FMT: Return a string that can be used as a format string for strftime(3) to represent a date in a locale-specific way.

T_FMT: Return a string that can be used as a format string for strftime(3) to represent a time in a locale-specific way.

T_FMT_AMPM: The return value can be used as a format string for `strftime' to represent time in the am/pm format.

DAY_1 ... DAY_7: Return name of the n-th day of the week. Warning: 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.

ABDAY_1 ... ABDAY_7: Return abbreviated name of the n-th day of the week.

MON_1 ... MON_12: Return name of the n-th month.

ABMON_1 ... ABMON_12: Return abbreviated name of the n-th month.

RADIXCHAR: Return radix character (decimal dot, decimal comma, etc.)

THOUSEP: Return separator character for thousands (groups of three digits).

YESEXPR: Return a regular expression that can be used with the regex function to recognize a positive response to a yes/no question. Warning: The expression is in the syntax suitable for the regex() function from the C library, which might differ from the syntax used in re.

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

CRNCYSTR: Return 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.

ERA

The return value represents the era used in the current 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 strftime function to use this information. The format of the returned string is not specified, and therefore you should not assume knowledge of it on different systems.

ERA_YEAR: The return value gives the year in the relevant era of the locale.

ERA_D_T_FMT: This return value can be used as a format string for strftime to represent dates and times in a locale-specific era-based way.

ERA_D_FMT: This return value can be used as a format string for strftime to represent time in a locale-specific era-based way.

ALT_DIGITS: The return value is a representation of up to 100 values used to represent the values 0 to 99.

Example:

>>> import locale
>>> loc = locale.getlocale(locale.LC_ALL) # get current locale
>>> locale.setlocale(locale.LC_ALL, 'de_DE') # use German locale; name might vary with platform
>>> 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

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