locale — Cultural Localization API

Purpose:Format and parse values that depend on location or language.

The locale module is part of Python’s internationalization and localization support library. It provides a standard way to handle operations that may depend on the language or location of a user. For example, it handles formatting numbers as currency, comparing strings for sorting, and working with dates. It does not cover translation (see the gettext module) or Unicode encoding (see the codecs module).

Note

Changing the locale can have application-wide ramifications, so the recommended practice is to avoid changing the value in a library and to let the application set it one time. In the examples in this section, the locale is changed several times within a short program to highlight the differences in the settings of various locales. It is far more likely that an application will set the locale once as it starts up or when a web request is received and not change it.

This section covers some of the high-level functions in the locale module. There are others which are lower level (format_string()) or which relate to managing the locale for an application (resetlocale()).

Probing the Current Locale

The most common way to let the user change the locale settings for an application is through an environment variable (LC_ALL, LC_CTYPE, LANG, or LANGUAGE, depending on the platform). The application then calls setlocale() without a hard-coded value, and the environment value is used.

locale_env.py
import locale
import os
import pprint

# Default settings based on the user's environment.
locale.setlocale(locale.LC_ALL, '')

print('Environment settings:')
for env_name in ['LC_ALL', 'LC_CTYPE', 'LANG', 'LANGUAGE']:
    print('\t{} = {}'.format(
        env_name, os.environ.get(env_name, ''))
    )

# What is the locale?
print('\nLocale from environment:', locale.getlocale())

template = """
Numeric formatting:

  Decimal point      : "{decimal_point}"
  Grouping positions : {grouping}
  Thousands separator: "{thousands_sep}"

Monetary formatting:

  International currency symbol   : "{int_curr_symbol!r}"
  Local currency symbol           : {currency_symbol!r}
  Symbol precedes positive value  : {p_cs_precedes}
  Symbol precedes negative value  : {n_cs_precedes}
  Decimal point                   : "{mon_decimal_point}"
  Digits in fractional values     : {frac_digits}
  Digits in fractional values,
                   international  : {int_frac_digits}
  Grouping positions              : {mon_grouping}
  Thousands separator             : "{mon_thousands_sep}"
  Positive sign                   : "{positive_sign}"
  Positive sign position          : {p_sign_posn}
  Negative sign                   : "{negative_sign}"
  Negative sign position          : {n_sign_posn}

"""

sign_positions = {
    0: 'Surrounded by parentheses',
    1: 'Before value and symbol',
    2: 'After value and symbol',
    3: 'Before value',
    4: 'After value',
    locale.CHAR_MAX: 'Unspecified',
}

info = {}
info.update(locale.localeconv())
info['p_sign_posn'] = sign_positions[info['p_sign_posn']]
info['n_sign_posn'] = sign_positions[info['n_sign_posn']]

print(template.format(**info))

The localeconv() method returns a dictionary containing the locale’s conventions. The full list of value names and definitions is covered in the standard library documentation.

A Mac running OS X 10.11.6 with all of the variables unset produces this output:

$ export LANG=; export LC_CTYPE=; python3 locale_env.py

Environment settings:
        LC_ALL =
        LC_CTYPE =
        LANG =
        LANGUAGE =

Locale from environment: (None, None)

Numeric formatting:

  Decimal point      : "."
  Grouping positions : []
  Thousands separator: ""

Monetary formatting:

  International currency symbol   : "''"
  Local currency symbol           : ''
  Symbol precedes positive value  : 127
  Symbol precedes negative value  : 127
  Decimal point                   : ""
  Digits in fractional values     : 127
  Digits in fractional values,
                   international  : 127
  Grouping positions              : []
  Thousands separator             : ""
  Positive sign                   : ""
  Positive sign position          : Unspecified
  Negative sign                   : ""
  Negative sign position          : Unspecified

Running the same script with the LANG variable set shows how the locale and default encoding change.

The United States (en_US):

$ LANG=en_US LC_CTYPE=en_US LC_ALL=en_US python3 locale_env.py

Environment settings:
        LC_ALL = en_US
        LC_CTYPE = en_US
        LANG = en_US
        LANGUAGE =

Locale from environment: ('en_US', 'ISO8859-1')

Numeric formatting:

  Decimal point      : "."
  Grouping positions : [3, 3, 0]
  Thousands separator: ","

Monetary formatting:

  International currency symbol   : "'USD '"
  Local currency symbol           : '$'
  Symbol precedes positive value  : 1
  Symbol precedes negative value  : 1
  Decimal point                   : "."
  Digits in fractional values     : 2
  Digits in fractional values,
                   international  : 2
  Grouping positions              : [3, 3, 0]
  Thousands separator             : ","
  Positive sign                   : ""
  Positive sign position          : Before value and symbol
  Negative sign                   : "-"
  Negative sign position          : Before value and symbol

France (fr_FR):

$ LANG=fr_FR LC_CTYPE=fr_FR LC_ALL=fr_FR python3 locale_env.py

Environment settings:
        LC_ALL = fr_FR
        LC_CTYPE = fr_FR
        LANG = fr_FR
        LANGUAGE =

Locale from environment: ('fr_FR', 'ISO8859-1')

Numeric formatting:

  Decimal point      : ","
  Grouping positions : [127]
  Thousands separator: ""

Monetary formatting:

  International currency symbol   : "'EUR '"
  Local currency symbol           : 'Eu'
  Symbol precedes positive value  : 0
  Symbol precedes negative value  : 0
  Decimal point                   : ","
  Digits in fractional values     : 2
  Digits in fractional values,
                   international  : 2
  Grouping positions              : [3, 3, 0]
  Thousands separator             : " "
  Positive sign                   : ""
  Positive sign position          : Before value and symbol
  Negative sign                   : "-"
  Negative sign position          : After value and symbol

Spain (es_ES):

$ LANG=es_ES LC_CTYPE=es_ES LC_ALL=es_ES python3 locale_env.py

Environment settings:
        LC_ALL = es_ES
        LC_CTYPE = es_ES
        LANG = es_ES
        LANGUAGE =

Locale from environment: ('es_ES', 'ISO8859-1')

Numeric formatting:

  Decimal point      : ","
  Grouping positions : [127]
  Thousands separator: ""

Monetary formatting:

  International currency symbol   : "'EUR '"
  Local currency symbol           : 'Eu'
  Symbol precedes positive value  : 0
  Symbol precedes negative value  : 0
  Decimal point                   : ","
  Digits in fractional values     : 2
  Digits in fractional values,
                   international  : 2
  Grouping positions              : [3, 3, 0]
  Thousands separator             : "."
  Positive sign                   : ""
  Positive sign position          : Before value and symbol
  Negative sign                   : "-"
  Negative sign position          : Before value and symbol

Portugal (pt_PT):

$ LANG=pt_PT LC_CTYPE=pt_PT LC_ALL=pt_PT python3 locale_env.py

Environment settings:
        LC_ALL = pt_PT
        LC_CTYPE = pt_PT
        LANG = pt_PT
        LANGUAGE =

Locale from environment: ('pt_PT', 'ISO8859-1')

Numeric formatting:

  Decimal point      : ","
  Grouping positions : []
  Thousands separator: " "

Monetary formatting:

  International currency symbol   : "'EUR '"
  Local currency symbol           : 'Eu'
  Symbol precedes positive value  : 0
  Symbol precedes negative value  : 0
  Decimal point                   : "."
  Digits in fractional values     : 2
  Digits in fractional values,
                   international  : 2
  Grouping positions              : [3, 3, 0]
  Thousands separator             : "."
  Positive sign                   : ""
  Positive sign position          : Before value and symbol
  Negative sign                   : "-"
  Negative sign position          : Before value and symbol

Poland (pl_PL):

$ LANG=pl_PL LC_CTYPE=pl_PL LC_ALL=pl_PL python3 locale_env.py

Environment settings:
        LC_ALL = pl_PL
        LC_CTYPE = pl_PL
        LANG = pl_PL
        LANGUAGE =

Locale from environment: ('pl_PL', 'ISO8859-2')

Numeric formatting:

  Decimal point      : ","
  Grouping positions : [3, 3, 0]
  Thousands separator: " "

Monetary formatting:

  International currency symbol   : "'PLN '"
  Local currency symbol           : 'zł'
  Symbol precedes positive value  : 1
  Symbol precedes negative value  : 1
  Decimal point                   : ","
  Digits in fractional values     : 2
  Digits in fractional values,
                   international  : 2
  Grouping positions              : [3, 3, 0]
  Thousands separator             : " "
  Positive sign                   : ""
  Positive sign position          : After value
  Negative sign                   : "-"
  Negative sign position          : After value

Currency

The earlier example output shows that changing the locale updates the currency symbol setting and the character to separate whole numbers from decimal fractions. This example loops through several different locales to print a positive and negative currency value formatted for each locale.

locale_currency.py
import locale

sample_locales = [
    ('USA', 'en_US'),
    ('France', 'fr_FR'),
    ('Spain', 'es_ES'),
    ('Portugal', 'pt_PT'),
    ('Poland', 'pl_PL'),
]

for name, loc in sample_locales:
    locale.setlocale(locale.LC_ALL, loc)
    print('{:>10}: {:>10}  {:>10}'.format(
        name,
        locale.currency(1234.56),
        locale.currency(-1234.56),
    ))

The output is this small table:

$ python3 locale_currency.py

       USA:   $1234.56   -$1234.56
    France: 1234,56 Eu  1234,56 Eu-
     Spain: 1234,56 Eu  -1234,56 Eu
  Portugal: 1234.56 Eu  -1234.56 Eu
    Poland: zł 1234,56  zł 1234,56-

Formatting Numbers

Numbers not related to currency are also formatted differently depending on the locale. In particular, the grouping character used to separate large numbers into readable chunks changes.

locale_grouping.py
import locale

sample_locales = [
    ('USA', 'en_US'),
    ('France', 'fr_FR'),
    ('Spain', 'es_ES'),
    ('Portugal', 'pt_PT'),
    ('Poland', 'pl_PL'),
]

print('{:>10} {:>10} {:>15}'.format(
    'Locale', 'Integer', 'Float')
)
for name, loc in sample_locales:
    locale.setlocale(locale.LC_ALL, loc)

    print('{:>10}'.format(name), end=' ')
    print(locale.format('%10d', 123456, grouping=True), end=' ')
    print(locale.format('%15.2f', 123456.78, grouping=True))

To format numbers without the currency symbol, use format() instead of currency().

$ python3 locale_grouping.py

    Locale    Integer           Float
       USA    123,456      123,456.78
    France     123456       123456,78
     Spain     123456       123456,78
  Portugal     123456       123456,78
    Poland    123 456      123 456,78

To convert locale-formatted numbers to a normalized locale-agnostic format, use delocalize().

locale_delocalize.py
import locale

sample_locales = [
    ('USA', 'en_US'),
    ('France', 'fr_FR'),
    ('Spain', 'es_ES'),
    ('Portugal', 'pt_PT'),
    ('Poland', 'pl_PL'),
]

for name, loc in sample_locales:
    locale.setlocale(locale.LC_ALL, loc)
    localized = locale.format('%0.2f', 123456.78, grouping=True)
    delocalized = locale.delocalize(localized)
    print('{:>10}: {:>10}  {:>10}'.format(
        name,
        localized,
        delocalized,
    ))

Grouping punctuation is removed and the decimal separator is converted to always be a ..

$ python3 locale_delocalize.py

       USA: 123,456.78   123456.78
    France:  123456,78   123456.78
     Spain:  123456,78   123456.78
  Portugal:  123456,78   123456.78
    Poland: 123 456,78   123456.78

Parsing Numbers

Besides generating output in different formats, the locale module helps with parsing input. It includes atoi() and atof() functions for converting the strings to integer and floating point values based on the locale’s numerical formatting conventions.

locale_atof.py
import locale

sample_data = [
    ('USA', 'en_US', '1,234.56'),
    ('France', 'fr_FR', '1234,56'),
    ('Spain', 'es_ES', '1234,56'),
    ('Portugal', 'pt_PT', '1234.56'),
    ('Poland', 'pl_PL', '1 234,56'),
]

for name, loc, a in sample_data:
    locale.setlocale(locale.LC_ALL, loc)
    print('{:>10}: {:>9} => {:f}'.format(
        name,
        a,
        locale.atof(a),
    ))

The grouping and decimal separator values of the locale are recognized by the parser.

$ python3 locale_atof.py

       USA:  1,234.56 => 1234.560000
    France:   1234,56 => 1234.560000
     Spain:   1234,56 => 1234.560000
  Portugal:   1234.56 => 1234.560000
    Poland:  1 234,56 => 1234.560000

Dates and Times

Another important aspect of localization is date and time formatting.

locale_date.py
import locale
import time

sample_locales = [
    ('USA', 'en_US'),
    ('France', 'fr_FR'),
    ('Spain', 'es_ES'),
    ('Portugal', 'pt_PT'),
    ('Poland', 'pl_PL'),
]

for name, loc in sample_locales:
    locale.setlocale(locale.LC_ALL, loc)
    format = locale.nl_langinfo(locale.D_T_FMT)
    print('{:>10}: {}'.format(name, time.strftime(format)))

This example uses the date formatting string for the locale to print the current date and time.

$ python3 locale_date.py

       USA: Fri Aug  5 17:33:31 2016
    France: Ven  5 aoû 17:33:31 2016
     Spain: vie  5 ago 17:33:31 2016
  Portugal: Sex  5 Ago 17:33:31 2016
    Poland: ptk  5 sie 17:33:31 2016

See also