Initial revision of gettext support for Python. This will undergo
some changes.
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Barry Warsaw
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"""Internationalization and localization support.
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This module provides internationalization (I18N) and localization (L10N)
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support for your Python programs by providing an interface to the GNU gettext
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message catalog library.
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I18N refers to the operation by which a program is made aware of multiple
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languages. L10N refers to the adaptation of your program, once
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internationalized, to the local language and cultural habits. In order to
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provide multilingual messages for your Python programs, you need to take the
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following steps:
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- prepare your program by specially marking translatable strings
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- run a suite of tools over your marked program files to generate raw
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messages catalogs
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- create language specific translations of the message catalogs
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- use this module so that message strings are properly translated
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In order to prepare your program for I18N, you need to look at all the strings
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in your program. Any string that needs to be translated should be marked by
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wrapping it in _('...') -- i.e. a call to the function `_'. For example:
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filename = 'mylog.txt'
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message = _('writing a log message')
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fp = open(filename, 'w')
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fp.write(message)
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fp.close()
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In this example, the string `writing a log message' is marked as a candidate
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for translation, while the strings `mylog.txt' and `w' are not.
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The GNU gettext package provides a tool, called xgettext, that scans C and C++
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source code looking for these specially marked strings. xgettext generates
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what are called `.pot' files, essentially structured human readable files
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which contain every marked string in the source code. These .pot files are
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copied and handed over to translators who write language-specific versions for
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every supported language.
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For I18N Python programs however, xgettext won't work; it doesn't understand
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the myriad of string types support by Python. The standard Python
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distribution provides a tool called pygettext that does though (found in the
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Tools/i18n directory). This is a command line script that supports a similar
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interface as xgettext; see its documentation for details. Once you've used
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pygettext to create your .pot files, you can use the standard GNU gettext
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tools to generate your machine-readable .mo files, which are what's used by
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this module.
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In the simple case, to use this module then, you need only add the following
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bit of code to the main driver file of your application:
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import gettext
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gettext.install()
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This sets everything up so that your _('...') function calls Just Work. In
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other words, it installs `_' in the builtins namespace for convenience. You
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can skip this step and do it manually by the equivalent code:
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import gettext
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import __builtin__
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__builtin__['_'] = gettext.gettext
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Once you've done this, you probably want to call bindtextdomain() and
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textdomain() to get the domain set up properly. Again, for convenience, you
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can pass the domain and localedir to install to set everything up in one fell
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swoop:
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import gettext
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gettext.install('mydomain', '/my/locale/dir')
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If your program needs to support many languages at the same time, you will
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want to create Translation objects explicitly, like so:
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import gettext
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gettext.install()
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lang1 = gettext.Translations(open('/path/to/my/lang1/messages.mo'))
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lang2 = gettext.Translations(open('/path/to/my/lang2/messages.mo'))
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lang3 = gettext.Translations(open('/path/to/my/lang3/messages.mo'))
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gettext.set(lang1)
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# all _() will now translate to language 1
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gettext.set(lang2)
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# all _() will now translate to language 2
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Currently, only GNU gettext format binary .mo files are supported.
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"""
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# This module represents the integration of work from the following authors:
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#
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# Martin von Loewis, who wrote the initial implementation of the underlying
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# C-based libintlmodule (later renamed _gettext), along with a skeletal
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# gettext.py implementation.
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#
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# Peter Funk, who wrote fintl.py, a fairly complete wrapper around intlmodule,
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# which also included a pure-Python implementation to read .mo files if
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# intlmodule wasn't available.
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#
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# James Henstridge, who also wrote a gettext.py module, which has some
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# interesting, but currently unsupported experimental features: the notion of
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# a Catalog class and instances, and the ability to add to a catalog file via
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# a Python API.
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#
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# Barry Warsaw integrated these modules, wrote the .install() API and code,
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# and conformed all C and Python code to Python's coding standards.
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import os
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import sys
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import struct
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from UserDict import UserDict
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# globals
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_translations = {}
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_current_translation = None
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_current_domain = 'messages'
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# Domain to directory mapping, for use by bindtextdomain()
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_localedirs = {}
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class GNUTranslations(UserDict):
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# Magic number of .mo files
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MAGIC = 0x950412de
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def __init__(self, fp):
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if fp is None:
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d = {}
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else:
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d = self._parse(fp)
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UserDict.__init__(self, d)
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def _parse(self, fp):
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"""Override this method to support alternative .mo formats."""
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unpack = struct.unpack
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filename = getattr(fp, 'name', '')
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# Parse the .mo file header, which consists of 5 little endian 32
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# bit words.
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catalog = {}
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buf = fp.read()
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magic, version, msgcount, masteridx, transidx = unpack(
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'<5i', buf[:20])
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if magic <> self.MAGIC:
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raise IOError(0, 'Bad magic number', filename)
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#
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# Now put all messages from the .mo file buffer into the catalog
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# dictionary.
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for i in xrange(0, msgcount):
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mstart = unpack('<i', buf[masteridx+4:masteridx+8])[0]
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mend = mstart + unpack('<i', buf[masteridx:masteridx+4])[0]
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tstart = unpack('<i', buf[transidx+4:transidx+8])[0]
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tend = tstart + unpack('<i', buf[transidx:transidx+4])[0]
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if mend < len(buf) and tend < len(buf):
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catalog[buf[mstart:mend]] = buf[tstart:tend]
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else:
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raise IOError(0, 'File is corrupt', filename)
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#
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# advance to next entry in the seek tables
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masteridx = masteridx + 8
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transidx = transidx + 8
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return catalog
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# By default, use GNU gettext format .mo files
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Translations = GNUTranslations
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# Locate a .mo file using the gettext strategy
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def _find(localedir=None, languages=None, category=None, domain=None):
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global _current_domain
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global _localedirs
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# Get some reasonable defaults for arguments that were not supplied
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if domain is None:
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domain = _current_domain
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if category is None:
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category = 'LC_MESSAGES'
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if localedir is None:
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localedir = _localedirs.get(
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domain,
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# TBD: The default localedir is actually system dependent. I
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# don't know of a good platform-consistent and portable way to
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# default it, so instead, we'll just use sys.prefix. Most
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# programs should be calling bindtextdomain() or such explicitly
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# anyway.
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os.path.join(sys.prefix, 'share', 'locale'))
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if languages is None:
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languages = []
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for envar in ('LANGUAGE', 'LC_ALL', 'LC_MESSAGES', 'LANG'):
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val = os.environ.get(envar)
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if val:
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languages = val.split(':')
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break
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if 'C' not in languages:
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languages.append('C')
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# select a language
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for lang in languages:
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if lang == 'C':
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break
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mofile = os.path.join(localedir, lang, category, '%s.mo' % domain)
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# see if it's in the cache
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mo = _translations.get(mofile)
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if mo:
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return mo
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fp = None
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try:
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try:
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fp = open(mofile, 'rb')
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t = Translations(fp)
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_translations[mofile] = t
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return t
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except IOError:
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pass
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finally:
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if fp:
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fp.close()
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return {}
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def bindtextdomain(domain=None, localedir=None):
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"""Bind domain to a file in the specified directory."""
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global _localedirs
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if domain is None:
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return None
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if localedir is None:
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return _localedirs.get(domain, _localedirs.get('C'))
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_localedirs[domain] = localedir
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return localedir
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def textdomain(domain=None):
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"""Change or query the current global domain."""
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global _current_domain
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if domain is None:
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return _current_domain
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else:
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_current_domain = domain
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return domain
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def gettext(message):
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"""Return localized version of a message."""
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return _find().get(message, message)
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def dgettext(domain, message):
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"""Like gettext(), but look up message in specified domain."""
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return _find(domain=domain).get(message, message)
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def dcgettext(domain, message, category):
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try:
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from locale import LC_CTYPE, LC_TIME, LC_COLLATE
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from locale import LC_MONETARY, LC_MESSAGES, LC_NUMERIC
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except ImportError:
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return message
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categories = {
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LC_CTYPE : 'LC_CTYPE',
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LC_TIME : 'LC_TIME',
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LC_COLLATE : 'LC_COLLATE',
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LC_MONETARY : 'LC_MONETARY',
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LC_MESSAGES : 'LC_MESSAGES',
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LC_NUMERIC : 'LC_NUMERIC'
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}
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return _find(domain=domain, category=category).get(message, message)
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# A higher level API
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def set(translation):
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global _current_translation
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_current_translation = translation
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def get():
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global _current_translation
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return _current_translation
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def install(domain=None, localedir=None):
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import __builtin__
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__builtin__.__dict__['_'] = gettext
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if domain is not None:
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bindtextdomain(domain, localedir)
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textdomain(domain)
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