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Support Classes and Functions
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The ``babel.support`` modules contains a number of classes and functions that
can help with integrating Babel, and internationalization in general, into your
application or framework. The code in this module is not used by Babel itself,
but instead is provided to address common requirements of applications that
should handle internationalization. 


---------------
Lazy Evaluation
---------------

One such requirement is lazy evaluation of translations. Many web-based
applications define some localizable message at the module level, or in general
at some level where the locale of the remote user is not yet known. For such
cases, web frameworks generally provide a "lazy" variant of the ``gettext``
functions, which basically translates the message not when the ``gettext``
function is invoked, but when the string is accessed in some manner.


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Extended Translations Class
---------------------------

Many web-based applications are composed of a variety of different components
(possibly using some kind of plugin system), and some of those components may
provide their own message catalogs that need to be integrated into the larger
system.

To support this usage pattern, Babel provides a ``Translations`` class that is
derived from the ``GNUTranslations`` class in the ``gettext`` module. This
class adds a ``merge()`` method that takes another ``Translations`` instance,
and merges the content of the latter into the main catalog:

.. code-block:: python

    translations = Translations.load('main')
    translations.merge(Translations.load('plugin1'))