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============================= i18n - Translations made easy ============================= This package tries to simplify the workflow and development of internationalized applications. It is a thin wrapper around existing tools, in particular gettext_ and babel_. .. _gettext: http://docs.python.org/library/gettext.html .. _babel: http://babel.edgewall.org/ Basic usage =========== :: # demo.py # from i18n.translator import Translator supported_languages = ['it_IT', 'fr_FR', 'de_DE'] # activate italian translations tr = Translator('/path/to/root', supported_languages, 'it_IT') print tr._('Hello world!') where ``/path/to/root/`` is the root directory of your project. When instantiated, the ``Translator`` class automatically creates a directory called ``/path/to/root/languages`` where the translations are stored. Extracting messages =================== Before doing the actual translation, you need to **extract** the messages from your source files, by invoking the ``extract`` command on the ``i18n`` module, which is a wrapper around ``pybabel extract`` and ``pybabel update``:: $ python -m i18n --root=/path/to/root --languages=it_IT,fr_FR,de_DE extract ``extract`` looks for all the messages wrapped inside calls to ``_()``, ``gettext()`` or ``ngettext()`` and produces a file called ``languages/template.pot``. This is a standard `gettext po file`` which contains all the messages found in the application. Moreover, ``extract()`` also creates a **message catalog** file for each of the supported languages as ``languages/$CODE/LC_MESSAGES/messages.po``, where ``$CODE`` is one of the languages listed in ``supported_languages`` (it_IT, fr_FR and de_DE in the example above). The catalog files are now ready to be translated using one of the many existing tools, for example `QT Linguist`_ or Poedit_. For the correct functioning of the application, the entire ``languages/`` hierarchy needs to be preserved. We suggest to track the various ``messages.po`` files in Version Control System together with the other files belonging to the application. .. _`QT Linguist`: http://qt.nokia.com/products/developer-tools?currentflipperobject=cf2f1a5149cecc583f8f2733206343ca#qt-tools-at-a .. _Poedit: http://www.poedit.net/ Updating messages ================= During the development of the application, you will surely add new messages to be translated. The ``extract`` command automatically handle this case: if it finds existing catalog files, their content (including the existing translations) is merged with the newly extracted messages. Compiling catalogs ================== It is necessary to compile the catalog files before using them with gettext. By default, our ``Translator`` object automatically compiles all the catalogs found in ``languages/``, producing the corresponding ``.mo`` files. The compilation is done only when the catalog file has been modified. This means that in most cases you do not have to worry about the compilation of the catalogs. If you prefer to have more control on this step, you can pass ``autocompile=False`` to the constructor of ``Translator`` and compile them manually from the command line:: $ python -m i18n --root=/path/to/root --languages=it_IT,fr_FR,de_DE compile Storing translations in a database ================================== For some applications it is useful to let the user to define new translations and/or override the default ones. ``i18n`` supports this use case with the ``DBTranslator`` class, which is a subclass of ``Translator``. When translating, ``DBTranslator`` first looks in the database: if the message is not found, it delegates to the standard gettext behavior. ``DBTranslator`` is based on sqlalchemy_. Its constructor takes an additional ``engine`` parameter:: from i18n.dbtranslator import DBTranslator from sqlalchemy import create_engine engine = create_engine('sqlite:///db.sqlite') ROOT = '/path/to/root' LANGUAGES = ['it_IT', 'fr_FR'] DEST_LANGUAGE = 'it_IT' tr = DBTranslator(ROOT, LANGUAGES, DEST_LANGUAGE, engine=engine) print tr._("hello world") ``DBTranslator`` automatically creates the table ``translation_entries`` in the DB. Then, it is up to the application to provide an user interface to manipulate the table. For testing, you can use the ``add_translation()`` method to insert a new translation in the DB:: tr.add_translation("it_IT", "hello world", "ciao mondo") print tr._("hello world") # prints "ciao mondo" .. _sqlalchemy: http://www.sqlalchemy.org/ How to use a global Translator ============================== By design, ``i18n`` tries to completely avoid any global state. This means that you can instantiate as many ``Translator`` and ``DBTranslator`` as you want, each one referring to a different directory and/or database. This is especially useful for testing. However, in practice most projects want to use a global translator which knows about the messages of all the components in the project. The demo application shows a way to do it in the ``translate.py`` module:: import py from i18n.translator import Translator # set the root of the project to the directory containing this file ROOT = py.path.local(__file__).dirpath() LANGUAGES = ['it_IT', 'fr_FR', 'de_DE'] tr = Translator(ROOT, LANGUAGES, 'it_IT') _ = tr._ ngettext = tr.ngettext if __name__ == '__main__': tr.cmdline(sys.argv) This way, the rest of the application can simply import and use ``_()`` and ``ngettext()`` from ``translate.py``. Or, at your preference, import directly the ``tr`` object and use ``tr._()`` and ``tr.ngettext()`` to translate messages. The last two lines of the code enables a convenient way to call ``extract`` and ``compile`` from the command line without having to manually specify the root dir and the supported languages. Just run:: $ python translate.py extract # ...or compile Acknowledgments ================ The development of this package has been generously funded by `S3 s.r.l.`_. .. _`S3 s.r.l.`: http://s3srl.com/