from jinja2 import Environment

env = Environment(extensions=['jinja2.ext.i18n'])
env.globals['gettext'] = {
    'Hello %(user)s!': 'Hallo %(user)s!'
}.__getitem__
env.globals['ngettext'] = lambda s, p, n: {
    '%(count)s user': '%(count)d Benutzer',
    '%(count)s users': '%(count)d Benutzer'
}[n == 1 and s or p]
print env.from_string("""\
{% trans %}Hello {{ user }}!{% endtrans %}
{% trans count=users|count %}{{ count }} user{% pluralize %}{{ count }} users{% endtrans %}
""").render(user="someone", users=[1, 2, 3])