2. i18n Extension¶

2.1. Environment Methods¶

After enabling the extension, the environment provides the following additional methods:

jinja2.Environment.install_gettext_translations(translations, newstyle=False)¶

Installs a translation globally for that environment. The translations object provided must implement at least ugettext and ungettext. The gettext.NullTranslations and gettext.GNUTranslations classes as well as Babels Translations class are supported.

Changed in version 2.5: newstyle gettext added

jinja2.Environment.install_null_translations(newstyle=False)¶

Install dummy gettext functions. This is useful if you want to prepare the application for internationalization but don’t want to implement the full internationalization system yet.

Changed in version 2.5: newstyle gettext added

jinja2.Environment.install_gettext_callables(gettext, ngettext, newstyle=False)¶

Installs the given gettext and ngettext callables into the environment as globals. They are supposed to behave exactly like the standard library’s gettext.ugettext() and gettext.ungettext() functions.

If newstyle is activated, the callables are wrapped to work like newstyle callables. See Newstyle Gettext for more information.

New in version 2.5.

jinja2.Environment.uninstall_gettext_translations()¶

Uninstall the translations again.

jinja2.Environment.extract_translations(source)¶

Extract localizable strings from the given template node or source.

For every string found this function yields a (lineno, function, message) tuple, where:

• lineno is the number of the line on which the string was found,
• function is the name of the gettext function used (if the string was extracted from embedded Python code), and
• message is the string itself (a unicode object, or a tuple of unicode objects for functions with multiple string arguments).

If Babel is installed, the babel integration can be used to extract strings for babel.

For a web application that is available in multiple languages but gives all the users the same language (for example a multilingual forum software installed for a French community) may load the translations once and add the translation methods to the environment at environment generation time:

translations = get_gettext_translations()
env = Environment(extensions=['jinja2.ext.i18n'])
env.install_gettext_translations(translations)

The get_gettext_translations function would return the translator for the current configuration. (For example by using gettext.find)

The usage of the i18n extension for template designers is covered as part of the template documentation.

2.2. Newstyle Gettext¶

Starting with version 2.5 you can use newstyle gettext calls. These are inspired by trac’s internal gettext functions and are fully supported by the babel extraction tool. They might not work as expected by other extraction tools in case you are not using Babel’s.

What’s the big difference between standard and newstyle gettext calls? In general they are less to type and less error prone. Also if they are used in an autoescaping environment they better support automatic escaping. Here are some common differences between old and new calls:

standard gettext:

{{ gettext('Hello World!') }}
{{ gettext('Hello %(name)s!')|format(name='World') }}
{{ ngettext('%(num)d apple', '%(num)d apples', apples|count)|format(
    num=apples|count
)}}

newstyle gettext looks like this instead:

{{ gettext('Hello World!') }}
{{ gettext('Hello %(name)s!', name='World') }}
{{ ngettext('%(num)d apple', '%(num)d apples', apples|count) }}

The advantages of newstyle gettext are that you have less to type and that named placeholders become mandatory. The latter sounds like a disadvantage but solves a lot of troubles translators are often facing when they are unable to switch the positions of two placeholder. With newstyle gettext, all format strings look the same.

Furthermore with newstyle gettext, string formatting is also used if no placeholders are used which makes all strings behave exactly the same. Last but not least are newstyle gettext calls able to properly mark strings for autoescaping which solves lots of escaping related issues many templates are experiencing over time when using autoescaping.