i18n – Helper functions for localizing text

This module provides facilities to faciliate the internationalization of applications using aioxmpp.

class aioxmpp.i18n.LocalizingFormatter(locale=None, tzinfo=None)

This is an alternative implementation on top of string.Formatter. It is designed to work well with babel, which also means that some things work differently when compared with the default string.Formatter.

Most notably, all objects from datetime are handled without using their __format__() method. Depending on their type, they are forwarded to the respective formatting method in babel.dates.

Type	Babel function	Timezone support
datetime	babel.dates.format_datetime()	yes
timedelta	babel.dates.format_timedelta()	no
date	babel.dates.format_date()	no
time	babel.dates.format_time()	no

If the format specification is empty, the default format as babel defines it is used.

In addition to date and time formatting, numbers which use the n format type are also formatted with babel. If the format specificaton is empty (except for the trailing n), babel.numbers.format_number() is used. Otherwise, the remainder of the format specification is passed as format to babel.numbers.format_decimal().

Examples:

>>> import pytz, babel, datetime, aioxmpp.i18n
>>> tz = pytz.timezone("Europe/Berlin")
>>> dt = datetime.datetime(year=2015, 5, 5, 15, 55, 55, tzinfo=tz)
>>> fmt = aioxmpp.i18n.LocalizingFormatter(locale=babel.Locale("en_GB"))
>>> fmt.format("{}", dt)
'5 May 2015 15:55:55'
>>> fmt.format("{:full}", dt)
'Tuesday, 5 May 2015 15:55:55 GMT+00:00'
>>> fmt.format("{:##.###n}, 120.3)
>>> fmt.format("{:##.###n}", 12.3)
'12.3'
>>> fmt.format("{:##.###;-(#)n}", -1.234)
'-(1.234)'
>>> fmt.format("{:n}", -10000)
'-10,000'

class aioxmpp.i18n.LocalizableString(singular, plural=None, number_index=None)

This class can be used for lazily translated localizable strings.

singular must be a str. If plural is not set, the string will be localized using gettext; otherwise, ngettext will be used. The detailed process on localizing a string is described in the documentation of localize().

Localizable strings compare equal if their singular, plural and number_index values all match. The str() of a localizable string is its singular string. The repr() depends on whether plural is set and refers to the usage of _() and ngettext().

The arguments are stored in attributes named like the arguments. LocalizableString instances are immutable and hashable.

Examples:

>>> import aioxmpp.i18n, pytz, babel, gettext
>>> fmt = aioxmpp.i18n.LocalizingFormatter()
>>> translator = gettext.NullTranslations()
>>> s1 = aioxmpp.i18n.LocalizableString(
...     "{count} thing",
...     "{count} things", "count")
>>> s1.localize(fmt, translator, count=1)
'1 thing'
>>> s1.localize(fmt, translator, count=10)
'10 things'

localize(formatter, translator, *args, **kwargs)

Localize and format the string using the given formatter and translator. The remaining args are passed to the format() method of the formatter.

The translator must be an object supporting the gettext.NullTranslations interface.

If plural is not None, the number which will be passed to the ngettext method of translator is first extracted from the args or kwargs, depending on number_index. The whole semantics of all three are described in string.Formatter.get_field(), which is used by this method (number_index is passed as field_name).

The value returned by get_field() is then used as third argument to ngettext, while the others are sourced from singular and plural.

If plural is None, the gettext method of translator is used with singular as its only argument.

After the translation step, the formatter is used with the translated string and args and kwargs to obtain a formatted version of the string which is then returned.

All of this works best when using a LocalizingFormatter.

Shorthand functions

aioxmpp.i18n._(s)

Return a new singular LocalizableString using s as singular form.

aioxmpp.i18n.ngettext(singular, plural, number_index)

Return a new plural LocalizableString with the given arguments; these are passed to the constructor of LocalizableString.