String substitution in message ids

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

Plone content classes inherit translate() function which can be used to get the final translated string. It will use the currently activate language. Translation domain will be taken from the msgid object itself, which is string-like zope.i18nmessageid instance.

Message ids are immutable (read-only) objects so you need to always create a new message id if you use different variable substituion mappings.

Python code:

from yourcompany.app import appMessageFactory as _

class SomeView(BrowserView):


    def do_stuff(self):

        msgid = _(u"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 = self.context.translate(msgid)

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

Corresponding .po file entry:

#. Default: "Found ${results} results"
#: ./browser/accommondationsummaryview.py:429
msgid "search_results_found_msg"
msgstr "Löytyi ${results} majoituskohdetta"

For more information, see

• http://wiki.zope.org/zope3/TurningMessageIDsIntoRocks