Source code: Lib/locale.py
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:
locale.
Error
¶Exception raised when the locale passed to
setlocale[]
is not recognized.
locale.
setlocale
[category, locale=None]¶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. locale may be a string, or an iterable of two strings [language code and encoding]. If it’s an iterable, it’s converted to a locale name using the locale aliasing engine. 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.
locale.
localeconv
[]¶Returns the database of the local conventions as a dictionary. This dictionary has the following strings as keys:
|
| Decimal point character. |
| Sequence of numbers specifying which relative positions the | |
| Character used between groups. | |
|
| International currency symbol. |
| Local currency symbol. | |
| Whether the currency symbol precedes the value [for positive resp. negative values]. | |
| Whether the currency symbol is separated from the value by a space [for positive resp. negative values]. | |
| Decimal point used for monetary values. | |
| Number of fractional digits used in local formatting of monetary values. | |
| Number of fractional digits used in international formatting of monetary values. | |
| Group separator used for monetary values. | |
| Equivalent to | |
| Symbol used to annotate a positive monetary value. | |
| Symbol used to annotate a negative monetary value. | |
| The position of the sign [for positive resp. negative values], see below. |
All numeric values can be set to CHAR_MAX
to indicate that there is no value specified in this locale.
The possible values for 'p_sign_posn'
and 'n_sign_posn'
are given below.
| Currency and value are surrounded by parentheses. |
| The sign should precede the value and currency symbol. |
| The sign should follow the value and currency symbol. |
| The sign should immediately precede the value. |
| The sign should immediately follow the value. |
| Nothing is specified in this locale. |
The function sets temporarily the LC_CTYPE
locale to the LC_NUMERIC
locale or the LC_MONETARY
locale if locales are different and numeric or monetary strings are non-ASCII. This temporary change affects other threads.
Changed in version 3.7: The function now sets temporarily the LC_CTYPE
locale to the LC_NUMERIC
locale in some cases.
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.
The nl_langinfo[]
function accepts one of the following keys. Most descriptions are taken from the corresponding description in the GNU C library.
locale.
CODESET
¶Get a string with the name of the character encoding used in the selected locale.
locale.
D_T_FMT
¶Get a string that can be used as a format string for time.strftime[]
to represent date and time in a locale-specific way.
locale.
D_FMT
¶Get a string that can be used as a format string for time.strftime[]
to represent a date in a locale-specific way.
locale.
T_FMT
¶Get a string that can be used as a format string for time.strftime[]
to represent a time in a locale-specific way.
locale.
T_FMT_AMPM
¶Get a format string for time.strftime[]
to represent time in the am/pm format.
DAY_1 ... DAY_7
Get the name of the n-th day of the week.
Note
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
Get the abbreviated name of the n-th day of the week.
MON_1 ... MON_12
Get the name of the n-th month.
ABMON_1 ... ABMON_12
Get the abbreviated name of the n-th month.
locale.
RADIXCHAR
¶Get the radix character [decimal dot, decimal comma, etc.].
locale.
THOUSEP
¶Get the separator character for thousands [groups of three digits].
locale.
YESEXPR
¶Get a regular expression that can be used with the regex function to recognize a positive response to a yes/no question.
Note
The expression is in the syntax suitable for the regex[]
function from the C library, which might differ from the syntax used in
re
.
locale.
NOEXPR
¶Get a regular expression that can be used with the regex[3] function to recognize a negative response to a yes/no question.
locale.
CRNCYSTR
¶Get 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.
locale.
ERA
¶Get a string that 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 time.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.
locale.
ERA_D_T_FMT
¶Get a format string for time.strftime[]
to represent date and time in a locale-specific era-based way.
locale.
ERA_D_FMT
¶Get a format string for time.strftime[]
to represent a date in a locale-specific era-based way.
locale.
ERA_T_FMT
¶Get a format string for time.strftime[]
to represent a time in a locale-specific era-based way.
locale.
ALT_DIGITS
¶Get a representation of up to 100 values used to represent the values 0 to 99.
locale.
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 'LC_ALL'
, 'LC_CTYPE'
, 'LANG'
and 'LANGUAGE'
, 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.
locale.
getlocale
[category=LC_CTYPE]¶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.
locale.
getpreferredencoding
[do_setlocale=True]¶Return the locale 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
.
On Android or if the Python UTF-8 Mode is enabled, always return 'UTF-8'
, the locale encoding and the do_setlocale argument are ignored.
The Python preinitialization configures the LC_CTYPE locale. See also the filesystem encoding and error handler.
Changed in version 3.7: The function now always returns UTF-8
on Android or if the
Python UTF-8 Mode is enabled.
locale.
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[]
.
locale.
resetlocale
[category=LC_ALL]¶Sets the locale for category to the default setting.
The default setting is determined by calling
getdefaultlocale[]
. category defaults to LC_ALL
.
locale.
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.
locale.
strxfrm
[string]¶Transforms a string to one that can be used in locale-aware comparisons. For example, strxfrm[s1] >> import locale
>>> loc = locale.getlocale[] # get current locale
# use German locale; name might vary with platform
>>> locale.setlocale[locale.LC_ALL, 'de_DE']
>>> 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
Background, details, hints, tips and caveats¶
The C standard defines the locale as a program-wide property that may be relatively expensive to change. On top of that, some implementations are broken in such a way that frequent locale changes may cause core dumps. This makes the locale somewhat painful to use correctly.
Initially, when a program
is started, the locale is the C
locale, no matter what the user’s preferred locale is. There is one exception: the LC_CTYPE
category is changed at startup to set the current locale encoding to the user’s preferred locale encoding. The program must explicitly say that it wants the user’s preferred locale settings for other categories by calling setlocale[LC_ALL, '']
.
It is generally
a bad idea to call setlocale[]
in some library routine, since as a side effect it affects the entire program. Saving and restoring it is almost as bad: it is expensive and affects other threads that happen to run before the settings have been restored.
If, when coding a module for general use, you need a locale independent version of an operation that is affected by the locale
[such as certain formats used with time.strftime[]
], you will have to find a way to do it without using the standard library routine. Even better is convincing yourself that using locale settings is okay. Only as a last resort should you document that your module is not compatible with non-C
locale settings.
The only way to perform numeric operations according to the locale is to
use the special functions defined by this module: atof[]
, atoi[]
, format[]
,
str[]
.
There is no way to perform case conversions and character classifications according to the locale. For [Unicode] text strings these are done according to the character value only, while for byte strings, the conversions and classifications are done according to the ASCII value of the byte, and bytes whose high bit is set [i.e., non-ASCII bytes] are never converted or considered part of a character class such as letter or whitespace.
For extension writers and programs that embed Python¶
Extension modules should never call
setlocale[]
, except to find out what the current locale is. But since the return value can only be used portably to restore it, that is not very useful [except perhaps to find out whether or not the locale is C
].
When Python code uses the
locale
module to change the locale, this also affects the embedding application. If the embedding application doesn’t want this to happen, it should remove the _locale
extension module [which does all the work] from the table of built-in modules in the config.c
file, and make sure that the _locale
module is not accessible as a shared
library.
Access to message catalogs¶
locale.
gettext
[msg]¶
locale.
dgettext
[domain, msg]¶ locale.
dcgettext
[domain, msg,
category]¶ locale.
textdomain
[domain]¶
locale.
bindtextdomain
[domain, dir]¶The locale module exposes the C library’s gettext interface on systems that provide this interface. It consists of the functions gettext[]
, dgettext[]
, dcgettext[]
, textdomain[]
, bindtextdomain[]
, and bind_textdomain_codeset[]
. These are similar
to the same functions in the gettext
module, but use the C library’s binary format for message catalogs, and the C library’s search algorithms for locating message catalogs.
Python applications should normally find no need to invoke these functions, and should use
gettext
instead. A known exception to this rule are applications that link with additional C libraries which internally invoke gettext[]
or dcgettext[]
. For these applications, it may be necessary to bind the text domain, so that the libraries can properly locate their message catalogs.