The functionality Babel provides for internationalization (I18n) and localization (L10N) can be separated into two different aspects:
tools to build and work with
gettextmessage catalogs, and
a Python interface to the CLDR (Common Locale Data Repository), providing access to various locale display names, localized number and date formatting, etc.
While the Python standard library includes a
gettext module that
enables applications to use message catalogs, it requires developers to
build these catalogs using GNU tools such as
msgfmt. And while
xgettext does have support for extracting
messages from Python files, it does not know how to deal with other kinds
of files commonly found in Python web-applications, such as templates, nor
does it provide an easy extensibility mechanism to add such support.
Babel addresses this by providing a framework where various extraction
methods can be plugged in to a larger message extraction framework, and
also removes the dependency on the GNU
gettext tools for common tasks,
as these aren’t necessarily available on all platforms. See
Working with Message Catalogs for details on this aspect of Babel.
Furthermore, while the Python standard library does include support for
basic localization with respect to the formatting of numbers and dates
locale module, among others), this support is based on the
assumption that there will be only one specific locale used per process
(at least simultaneously.) Also, it doesn’t provide access to other kinds
of locale data, such as the localized names of countries, languages, or
time-zones, which are frequently needed in web-based applications.
For these requirements, Babel includes data extracted from the Common Locale Data Repository (CLDR), and provides a number of convenient methods for accessing and using this data. See Locale Data, Date and Time, and Number Formatting for more information on this aspect of Babel.