Stefan Seifert > Petal > Petal::I18N



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Petal::I18N - Attempt at implementing ZPT I18N for Petal


in your Perl code:

  use Petal;
  use Petal::TranslationService::Gettext;

  my $translation_service = new Petal::TranslationService::Gettext (
      locale_dir  => '/path/to/my/app/locale',
      target_lang => gimme_target_lang(), 

  my $template = new Petal (
      file => 'example.html',
      translation_service => $translation_service

  # we want to internationalize to the h4x0rz 31337 l4nGu4g3z. w00t!
  my $translation_service = Petal::TranslationService::h4x0r->new();
  my $template = new Petal (
      file => 'silly_example.xhtml',
      translation_service => $ts,

  print $template->process ();

I18N Howto ^

Preparing your templates:

Say your un-internationalized template looks like this:

  <html xmlns:tal="">
      <img src="/images/my_logo.png"
           alt="the logo of our organisation" />

         <span petal:content="user_name">Joe</span>.</p>

      <p>How are you today?</p>

You need to markup your template according to the ZPT I18N specification, which can be found at

  <html xmlns:tal=""
      <img src="/images/my_logo.png"
           alt="the logo of our organisation"
           i18n:attributes="alt" />
      <p i18n:translate="">Hello, <span petal:content="user_name">Joe</span>.</p>
      <p i18n:translate="">How are you today?</p>

Extracting I18N strings:

Once your templates are marked up properly, you will need to use a tool to extract the I18N strings into .pot (po template) files. To my knowledge you can use i18ndude (standalone python executable), (part of Zope 3), or I18NFool.

I use i18ndude to find strings which are not marked up properly with i18n:translate attributes and I18NFool for extracting strings and managing .po files.

Assuming you're using i18nfool:

  mkdir -p /path/to/my/app/locale
  cd /path/to/my/app/locale
  i18nfool-extract /path/to/my/template/example.html
  mkdir en
  mkdir fr
  mkdir es

Then you translate the .po files into their respective target languages. When that's done, you type:

  cd /path/to/my/app/locale

And it builds all the .mo files.

Making your application use a Gettext translation service:

Previously you might have had:

  use Petal;
  # lotsa code here
  my $template = Petal->new ('example.html');

This needs to become:

  use Petal;
  use Petal::TranslationService::Gettext;
  # lotsa code here
  my $template = Petal->new ('example.html');
  $template->{translation_service} = Petal::TranslationService::Gettext->new (
      locale_dir  => '/path/to/my/app/locale',
      target_lang => gimme_language_code(),

Where gimme_language_code() returns a language code depending on LC_LANG, content-negotiation, config-file, or whatever mechanism you are using to decide which language is desired.

And then?

And then that's it! Your application should be easily internationalizable. There are a few traps / gotchas thought, which are described below.

BUGS, TRAPS, GOTCHAS and other niceties ^

Translation Phase

The translation step takes place ONLY ONCE THE TEMPLATE HAS BEEN PROCESSED.

So if you have:

  <p i18n:translate="">Hello,
    <span i18n:name="user_login" tal:replace="self/user_login">Joe</span>

It most likely will not work because the tal:replace would remove the <span> tag and also the i18n:name in the process.

This means that instead of receiving something such as:

  Hello, ${user_login}

The translation service would receive:

  Hello, Fred Flintstone


  Hello, Joe SixPack


To fix this issue, use tal:content instead of tal:replace and leave the span and its i18n:name attribute.

Character sets

I haven't worried too much about them (yet) so if you run into trouble join the Petal mailing list and we'll try to fix any issues together.


At the moment, Petal::I18N supports the following constructs:


It does *NOT* (well, not yet) support i18n:source, i18n:target or i18n:data.

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