Translating text strings#

Todo

This chapter may contains outdated or incorrect information. Please submit a pull request to make a correction.

Note

This chapter concerns only code-level translations of text strings.

For user-generated content translations, see Translating content.

This chapter describes how to translate Python and TAL template source code text strings using the gettext framework and other Plone/Zope i18n facilities.

Plone internally uses the UNIX standard gettext tool to perform i18n.

zope.i18n#

The package zope.i18n implements several APIs related to internationalization and localization.

  • Follows gettext best practices.

  • Translations are stored in the locales folder of your application, such as locales/fi/LC_MESSAGES/your.app.po.

  • Uses the package zope.i18nmessageid. This provides a string-like class which allows storing the translation domain with translatable text strings.

  • PO files must usually be manually converted to binary MO files every time the translations are updated. See i18ndude. It is also possible to set an environment variable to trigger recompilation of MO files. See i18ndude below for details.

See also

zope.i18n on PyPI

Plone searches only the filename and path for the translation files. Information in the PO file headers is ignored.

Generating a .pot template file for your packages#

i18ndude should be used to create a script which searches particular packages for translation strings.

If you have created your add-on using bobtemplates.plone, then you will already have a script update.sh inside your package and a script update_locale in your buildout to extract the messages from your code.

After running that script, a new domain.pot file will be created in your locales directory where all the messages will be saved.

To have those messages translated into some languages, you will need to create a language directory inside the locales directory, and a LC_MESSAGES directory inside it. This follows the gettext standard. After doing that, the directory structure will be as follows.

./locales/en/LC_MESSAGES/domain.po
./locales/fi/LC_MESSAGES/domain.po
./locales/ga/LC_MESSAGES/domain.po

You will need to provide your translations in those domain.po files.

If you add, update, or remove strings in your package, you will need to run only the update.sh script to update all language files.

You also need to have the following ZCML entry to signal Plone that the files stored in the locales folder follow the gettext standard and that it needs to use them when requesting translated strings.

<configure xmlns:i18n="http://namespaces.zope.org/i18n">
    <i18n:registerTranslations directory="locales" />
</configure>

Marking translatable strings in Python#

You will need to declare you own MessageFactory. This is a callable that marks strings with a translation domain. MessageFactory is usually declared in the main __init__.py file of your package. It is imported from wherever it is needed in your package. _ is the standard name that is used in gettext to identify the translation function, and the previous scripts will use that assumption to identify translatable strings.

from zope.i18nmessageid import MessageFactory

# your.app.package must match domain declaration in .po files
_ = MessageFactory('youpackage.name')

Now you can use the message factory to mark strings with translation domains.

from your.app.package import _
my_translatable_text = _("My text")

The object will still look like a string:

>>> my_translatable_text
u'My text'

But in reality, it is a zope.i18nmessageid.message.Message object:

>>> my_translatable_text.__class__
<type 'zope.i18nmessageid.message.Message'>

>>> my_translatable_text.domain
'your.app.package'

To see the translation in Python code you will need to manually call the translate function in zope.i18n:

>>> from zope.i18n import translate
>>> translate(my_translatable_text)
u"The text of the translation." # This is the corresponding msgstr from the .po file

Marking translatable strings in TAL page templates#

Declare the XML namespace i18n and translation domain at the beginning of your template, in the first element.

<div id="mobile-header" xmlns:i18n="http://xml.zope.org/namespaces/i18n" i18n:domain="plomobile">

Translate an element's text using i18n:translate="". It will use the text content of the element as msgid.

<li class="heading" i18n:translate="">
    Sections
</li>

Use attributes i18n:translate, i18n:attributes, and so on. For examples, look at any core Plone .pt files.

The i18n:translate attribute will hook into the translation machinery, and will look up the corresponding translated string to the one stated there, while looking in the relevant domain.po file corresponding to the i18n:domain stated in the file and the language negotiated by Plone.

Automatically translated message IDs#

Plone will automatically perform translation for message IDs which are output in page templates.

The following code translates my_translateable_text to the native language activated for the current page.

<span tal:content="view/my_translateable_text">

Note

Since my_translateable_text is a zope.i18nmessageid.message.Message instance containing its own gettext domain information, the i18n:domain attribute in page templates does not affect message IDs declared through message factories.

Manually translated message IDs#

If you need to manipulate translated text outside page templates, then you need to perform the final translation manually. This is needed when you are building human-readable strings in Python code, for example when creating some messages that are sent by email to the end user.

Translation always needs context. That means under which site the translation happens. The active language and other preferences are read from the HTTP request object and site object settings.

Translation should be performed using the zope.i18n.translate() method:

from zope.i18n import translate
from zope.globalrequest import getRequest
# Translate some text
msgid = _("My text") # my_text is zope.

# Use inherited translate() function to get the final text string
translated = translate(msgid, context=getRequest())

# translated is now u"Käännetty teksti" (in Finnish)

Non-Python message IDs#

There are other message ID markers in code outside the Python domain that have their own mechanisms:

  • ZCML entries

  • GenericSetup XML

  • TAL page templates

Translation string substitution#

Translation string substitutions must be used when the final translated message contains variable strings.

The translation domain will be taken from the msgid object itself, which is a string-like zope.i18nmessageid instance.

Message IDs are immutable (read-only) objects. You need to always create a new message ID if you use different variable substitution mappings. For example, in your view code, you would do the following.

from saariselka.app import _
from zope.i18n import translate
from zope.globalrequest import getRequest

class SomeView(BrowserView):

    def do_stuff(self):

        msgid = _("search_results_found_msg", default=u"Found ${results} results", mapping={u"results": len(self.contents)})

        # Use inherited translate() function to get the final text string
        translated = translate(msgid, context=getRequest())

        # Show the final result count to the user as a portal status message
        messages = IStatusMessage(self.request)
        messages.addStatusMessage(translated, type="info")

i18ndude#

i18ndude is a developer-oriented command-line utility to manage PO and MO files.

Usually you build our own shell script wrapper around i18ndude to automate generation of MO files from your package's PO files.

Plone will automatically compile all PO files to MO files on start up if a specific environment variable is enabled.

In your buildout.cfg in the part using plone.recipe.zope2instance, you can set an environment variable for this.

environment-vars =
    zope_i18n_compile_mo_files true

Note that the value does not matter. The code in zope.i18n looks for the mere existence of the variable, and does not care what is its value.

If you do not add that environment variable, you will need to provide the MO files in your package. To make this easier, and if you use zest.releaser to publish your packages, you can use zest.pocompile. This script hooks into the release process and builds the MO files for you.

Installing i18ndude#

The recommended method is to have i18ndude installed via your buildout.

Add the following to your buildout.cfg:

parts =
    ...
    i18ndude

[i18ndude]
unzip = true
recipe = zc.recipe.egg
eggs = i18ndude

After running buildout, i18ndude will be available in your buildout/bin folder.

bin/i18ndude -h
Usage: i18ndude command [options] [path | file1 file2 ...]]

You can also call it relative to your current package source folder.

server:home moo$  cd src/mfabrik.plonezohointegration/
server:mfabrik.plonezohointegration moo$ ../../bin/i18ndude

Setting up folder structure for Finnish and English#

Start by creating folders to hold the translation files.

mkdir locales
mkdir locales/fi
mkdir locales/en
mkdir locales/fi/LC_MESSAGES
mkdir locales/en/LC_MESSAGES

Creating .pot base file#

Example:

i18ndude rebuild-pot --pot locales/mydomain.pot --create your.app.package .

Manual PO entries#

i18ndude scans source .py and .pt files for translatable text strings. On some occasions this is not enough, for example, when you dynamically generate message IDs in your code. Entries which cannot be detected by an automatic code scan are called manual .po entries. They are managed in locales/manual.pot, which is merged into the generated locales/yournamespace.app.pot file.

Here is a sample manual.pot file.

msgstr ""
"Project-Id-Version: PACKAGE VERSION\n"
"MIME-Version: 1.0\n"
"Content-Type: text/plain; charset=utf-8\n"
"Content-Transfer-Encoding: 8bit\n"
"Plural-Forms: nplurals=1; plural=0\n"
"Preferred-Encodings: utf-8 latin1\n"
"Domain: mfabrik.app\n"

# This entry is used in gomobiletheme.mfabrik  templates for the campaign page header
# It is not automatically picked, since it is referred from external package
#. Default: "Watch video"
msgid "watch_video"
msgstr ""

Dynamic content#

If your HTML template has dynamic content similar to the following:

<h1 i18n:translate="search_form_heading">Search from <span tal:content="context/@@plone_portal_state/portal_title" /></h1>

…then it will produce a PO entry like this:

msgstr "Hae sivustolta <span>${DYNAMIC_CONTENT}</span>"

You need to give the name to the dynamic part so the PO file can handle it like a variable:

<h1 i18n:translate="search_form_heading">
Search from
<span i18n:name="site_title"
      tal:content="context/@@plone_portal_state/portal_title" /></h1>

And then you can refer to the dynamic part by its name:

#. Default: "Search from <span>${site_title}</span>"
#: ./skins/gomobiletheme_basic/search.pt:46
#: ./skins/gomobiletheme_plone3/search.pt:46
msgid "search_form_heading"
msgstr "Hae sivustolta ${site_title}"

See also

https://web.archive.org/web/20131018150303/http://permalink.gmane.org/gmane.comp.web.zope.plone.collective.cvs/111531

Overriding translations#

If you need to change a translation from a PO file, you could create a new Python package and register your own PO files.

To do this, create the package and add a locales directory in there, along the lines of what plone.app.locales does. Then you can add your own translations in the language that you need. For example, locales/fr/LC_MESSAGES/plone.po overrides French messages in the plone domain.

Reference the translation in configure.zcml of your package:

<configure xmlns:i18n="http://namespaces.zope.org/i18n"
           i18n_domain="my.package">
    <i18n:registerTranslations directory="locales" />
</configure>

Your ZCML needs to be included before the one from plone.app.locales. The first translation of a msgid wins. To manage this, you can include the ZCML in the buildout:

[instance]
recipe = plone.recipe.zope2instance
user = admin:admin
http-address = 8280
eggs =
    Plone
    my.package
    ${buildout:eggs}
environment-vars =
    zope_i18n_compile_mo_files true
# my.package is needed here so its configure.zcml
# is loaded before plone.app.locales
zcml = my.package

See the Overriding Translations section of Maurits van Rees's blog entry on Plone i18n.