Question

Inside a Django view, I create a subject like that:

subject = _(u"%(user)s has posted a comment") % { 'user': user }

Then I pass this subject to a function, which handles email notifications:

send_notifications(request, subject, url)

In send_notifications, I iterate over all subscriptions and send emails. However, each user can have a different language, so I activate the user’s language dynamically via Django’s activate:

def send_notifications(request, subject, url):
    from django.utils.translation import activate
    for s in Subscription.objects.filter(url=url):
        activate(s.user.userprofile.lang)
        send_mail(subject, render_to_string('notification_email.txt', locals()), settings.SERVER_EMAIL, [s.user.email])

The template gets rendered in the correct language of each user. However, the subject is passed as an evaluated and translated string to send_notifications and thus, is not translated.

I played around with lazy translations and lambda functions as parameters, but without success. Any help appreciated 🙂

Answer 1

Instead of passing the translated subject, just pass it non translated:

subject = '%(user)s has posted a comment'
context = {'user': user}

def send_notifications(request, subject, url, context):
    from django.utils.translation import activate
    for s in Subscription.objects.filter(url=url):
        activate(s.user.userprofile.lang)
        send_mail(_(subject) % context, render_to_string('notification_email.txt', locals()), settings.SERVER_EMAIL, [s.user.email])

If you’re not going to personalize the contents per user, then you might as well limit the number of renderings because that’s a little confusing:

# also do your imports at the top to catch import issues early
from django.utils.translation import activate
from django.utils.translation import ugettext as _

def send_notifications(request, url, 
    translatable_subject, context,
    body_template='notification_template.txt'):
    previous_lang = None
    for s in Subscription.objects.filter(url=url).order_by('user__userprofile__lang'):
        if s.user.userprofile.lang != previous_lang:
            activate(s.user.userprofile.lang)
            subject = _(translatable_subject) % context
            body = render_to_string(body_template, locals())
        send_mail(subject, body, settings.SERVER_EMAIL, [s.user.email])
        previous_lang = s.user.userprofile.lang

As such, it is much more obvious that you’re not going to render emails per usage.

This slight rewrite should make you doubt about the original choice of a couple of names (locals, notification_template).

The above sample code is barely an “educated guess” and you should double check it and make sure you understand everything before you paste it.