The functionality Babel provides for internationalization (I18n) and localization (L10N) can be separated into two different aspects:

  • tools to build and work with gettext message 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.

Message Catalogs

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 xgettext, msgmerge, and 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.

Locale Data

Furthermore, while the Python standard library does include support for basic localization with respect to the formatting of numbers and dates (the 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.