"""Internationalization and localization support.
This module provides internationalization (I18N) and localization (L10N)
support for your Python programs by providing an interface to the GNU gettext
message catalog library.
I18N refers to the operation by which a program is made aware of multiple
languages. L10N refers to the adaptation of your program, once
internationalized, to the local language and cultural habits.
"""
# This module represents the integration of work, contributions, feedback, and
# suggestions from the following people:
#
# Martin von Loewis, who wrote the initial implementation of the underlying
# C-based libintlmodule (later renamed _gettext), along with a skeletal
# gettext.py implementation.
#
# Peter Funk, who wrote fintl.py, a fairly complete wrapper around intlmodule,
# which also included a pure-Python implementation to read .mo files if
# intlmodule wasn't available.
#
# James Henstridge, who also wrote a gettext.py module, which has some
# interesting, but currently unsupported experimental features: the notion of
# a Catalog class and instances, and the ability to add to a catalog file via
# a Python API.
#
# Barry Warsaw integrated these modules, wrote the .install() API and code,
# and conformed all C and Python code to Python's coding standards.
#
# Francois Pinard and Marc-Andre Lemburg also contributed valuably to this
# module.
#
# J. David Ibanez implemented plural forms. Bruno Haible fixed some bugs.
#
# TODO:
# - Lazy loading of .mo files. Currently the entire catalog is loaded into
# memory, but that's probably bad for large translated programs. Instead,
# the lexical sort of original strings in GNU .mo files should be exploited
# to do binary searches and lazy initializations. Or you might want to use
# the undocumented double-hash algorithm for .mo files with hash tables, but
# you'll need to study the GNU gettext code to do this.
#
# - Support Solaris .mo file formats. Unfortunately, we've been unable to
# find this format documented anywhere.
import copy, os, re, struct, sys
from errno import ENOENT
__all__ = ['NullTranslations', 'GNUTranslations', 'Catalog',
'find', 'translation', 'install', 'textdomain', 'bindtextdomain',
'dgettext', 'dngettext', 'gettext', 'ngettext',
]
_default_localedir = os.path.join(sys.prefix, 'share', 'locale')
def test(condition, true, false):
"""
Implements the C expression:
condition ? true : false
Required to correctly interpret plural forms.
"""
if condition:
return true
else:
return false
def c2py(plural):
"""Gets a C expression as used in PO files for plural forms and returns a
Python lambda function that implements an equivalent expression.
"""
# Security check, allow only the "n" identifier
from StringIO import StringIO
import token, tokenize
tokens = tokenize.generate_tokens(StringIO(plural).readline)
try:
danger = [x for x in tokens if x[0] == token.NAME and x[1] != 'n']
except tokenize.TokenError:
raise ValueError, \
'plural forms expression error, maybe unbalanced parenthesis'
else:
if danger:
raise ValueError, 'plural forms expression could be dangerous'
# Replace some C operators by their Python equivalents
plural = plural.replace('&&', ' and ')
plural = plural.replace('||', ' or ')
expr = re.compile(r'\!([^=])')
plural = expr.sub(' not \\1', plural)
# Regular expression and replacement function used to transform
# "a?b:c" to "test(a,b,c)".
expr = re.compile(r'(.*?)\?(.*?):(.*)')
def repl(x):
return "test(%s, %s, %s)" % (x.group(1), x.group(2),
expr.sub(repl, x.group(3)))
# Code to transform the plural expression, taking care of parentheses
stack = ['']
for c in plural:
if c == '(':
stack.append('')
elif c == ')':
if len(stack) == 1:
# Actually, we never reach this code, because unbalanced
# parentheses get caught in the security check at the
# beginning.
raise ValueError, 'unbalanced parenthesis in plural form'
s = expr.sub(repl, stack.pop())
stack[-1] += '(%s)' % s
else:
stack[-1] += c
plural = expr.sub(repl, stack.pop())
return eval('lambda n: int(%s)' % plural)
def _expand_lang(locale):
from locale import normalize
locale = normalize(locale)
COMPONENT_CODESET = 1 << 0
COMPONENT_TERRITORY = 1 << 1
COMPONENT_MODIFIER = 1 << 2
# split up the locale into its base components
mask = 0
pos = locale.find('@')
if pos >= 0:
modifier = locale[pos:]
locale = locale[:pos]
mask |= COMPONENT_MODIFIER
else:
modifier = ''
pos = locale.find('.')
if pos >= 0:
codeset = locale[pos:]
locale = locale[:pos]
mask |= COMPONENT_CODESET
else:
codeset = ''
pos = locale.find('_')
if pos >= 0:
territory = locale[pos:]
locale = locale[:pos]
mask |= COMPONENT_TERRITORY
else:
territory = ''
language = locale
ret = []
for i in range(mask+1):
if not (i & ~mask): # if all components for this combo exist ...
val = language
if i & COMPONENT_TERRITORY: val += territory
if i & COMPONENT_CODESET: val += codeset
if i & COMPONENT_MODIFIER: val += modifier
ret.append(val)
ret.reverse()
return ret
class NullTranslations:
def __init__(self, fp=None):
self._info = {}
self._charset = None
self._fallback = None
if fp is not None:
self._parse(fp)
def _parse(self, fp):
pass
def add_fallback(self, fallback):
if self._fallback:
self._fallback.add_fallback(fallback)
else:
self._fallback = fallback
def gettext(self, message):
if self._fallback:
return self._fallback.gettext(message)
return message
def ngettext(self, msgid1, msgid2, n):
if self._fallback:
return self._fallback.ngettext(msgid1, msgid2, n)
if n == 1:
return msgid1
else:
return msgid2
def ugettext(self, message):
if self._fallback:
return self._fallback.ugettext(message)
return unicode(message)
def ungettext(self, msgid1, msgid2, n):
if self._fallback:
return self._fallback.ungettext(msgid1, msgid2, n)
if n == 1:
return unicode(msgid1)
else:
return unicode(msgid2)
def info(self):
return self._info
def charset(self):
return self._charset
def install(self, unicode=False):
import __builtin__
__builtin__.__dict__['_'] = unicode and self.ugettext or self.gettext
class GNUTranslations(NullTranslations):
# Magic number of .mo files
LE_MAGIC = 0x950412deL
BE_MAGIC = 0xde120495L
def _parse(self, fp):
"""Override this method to support alternative .mo formats."""
unpack = struct.unpack
filename = getattr(fp, 'name', '')
# Parse the .mo file header, which consists of 5 little endian 32
# bit words.
self._catalog = catalog = {}
self.plural = lambda n: int(n != 1) # germanic plural by default
buf = fp.read()
buflen = len(buf)
# Are we big endian or little endian?
magic = unpack('<I', buf[:4])[0]
if magic == self.LE_MAGIC:
version, msgcount, masteridx, transidx = unpack('<4I', buf[4:20])
ii = '<II'
elif magic == self.BE_MAGIC:
version, msgcount, masteridx, transidx = unpack('>4I', buf[4:20])
ii = '>II'
else:
raise IOError(0, 'Bad magic number', filename)
# Now put all messages from the .mo file buffer into the catalog
# dictionary.
for i in xrange(0, msgcount):
mlen, moff = unpack(ii, buf[masteridx:masteridx+8])
mend = moff + mlen
tlen, toff = unpack(ii, buf[transidx:transidx+8])
tend = toff + tlen
if mend < buflen and tend < buflen:
msg = buf[moff:mend]
tmsg = buf[toff:tend]
else:
raise IOError(0, 'File is corrupt', filename)
# See if we're looking at GNU .mo conventions for metadata
if mlen == 0:
# Catalog description
# don't handle multi-lines fields here, and skip
# lines which don't look like a header description
# (e.g. "header: value")
lastk = k = None
for item in tmsg.splitlines():
item = item.strip()
if not item or not ':' in item:
continue
k, v = item.split(':', 1)
k = k.strip().lower()
v = v.strip()
self._info[k] = v
if k == 'content-type':
self._charset = v.split('charset=')[1]
elif k == 'plural-forms':
v = v.split(';')
plural = v[1].split('plural=')[1]
self.plural = c2py(plural)
# Note: we unconditionally convert both msgids and msgstrs to
# Unicode using the character encoding specified in the charset
# parameter of the Content-Type header. The gettext documentation
# strongly encourages msgids to be us-ascii, but some appliations
# require alternative encodings (e.g. Zope's ZCML and ZPT). For
# traditional gettext applications, the msgid conversion will
# cause no problems since us-ascii should always be a subset of
# the charset encoding. We may want to fall back to 8-bit msgids
# if the Unicode conversion fails.
if msg.find('\x00') >= 0:
# Plural forms
msgid1, msgid2 = msg.split('\x00')
tmsg = tmsg.split('\x00')
if self._charset:
msgid1 = unicode(msgid1, self._charset)
tmsg = [unicode(x, self._charset) for x in tmsg]
for i in range(len(tmsg)):
catalog[(msgid1, i)] = tmsg[i]
else:
if self._charset:
msg = unicode(msg, self._charset)
tmsg = unicode(tmsg, self._charset)
catalog[msg] = tmsg
# advance to next entry in the seek tables
masteridx += 8
transidx += 8
def gettext(self, message):
missing = object()
tmsg = self._catalog.get(message, missing)
if tmsg is missing:
if self._fallback:
return self._fallback.gettext(message)
return message
# Encode the Unicode tmsg back to an 8-bit string, if possible
if self._charset:
return tmsg.encode(self._charset)
return tmsg
def ngettext(self, msgid1, msgid2, n):
try:
tmsg = self._catalog[(msgid1, self.plural(n))]
if self._charset:
return tmsg.encode(self._charset)
return tmsg
except KeyError:
if self._fallback:
return self._fallback.ngettext(msgid1, msgid2, n)
if n == 1:
return msgid1
else:
return msgid2
def ugettext(self, message):
missing = object()
tmsg = self._catalog.get(message, missing)
if tmsg is missing:
if self._fallback:
return self._fallback.ugettext(message)
return unicode(message)
return tmsg
def ungettext(self, msgid1, msgid2, n):
try:
tmsg = self._catalog[(msgid1, self.plural(n))]
except KeyError:
if self._fallback:
return self._fallback.ungettext(msgid1, msgid2, n)
if n == 1:
tmsg = unicode(msgid1)
else:
tmsg = unicode(msgid2)
return tmsg
# Locate a .mo file using the gettext strategy
def find(domain, localedir=None, languages=None, all=0):
# Get some reasonable defaults for arguments that were not supplied
if localedir is None:
localedir = _default_localedir
if languages is None:
languages = []
for envar in ('LANGUAGE', 'LC_ALL', 'LC_MESSAGES', 'LANG'):
val = os.environ.get(envar)
if val:
languages = val.split(':')
break
if 'C' not in languages:
languages.append('C')
# now normalize and expand the languages
nelangs = []
for lang in languages:
for nelang in _expand_lang(lang):
if nelang not in nelangs:
nelangs.append(nelang)
# select a language
if all:
result = []
else:
result = None
for lang in nelangs:
if lang == 'C':
break
mofile = os.path.join(localedir, lang, 'LC_MESSAGES', '%s.mo' % domain)
if os.path.exists(mofile):
if all:
result.append(mofile)
else:
return mofile
return result
# a mapping between absolute .mo file path and Translation object
_translations = {}
def translation(domain, localedir=None, languages=None,
class_=None, fallback=False):
if class_ is None:
class_ = GNUTranslations
mofiles = find(domain, localedir, languages, all=1)
if not mofiles:
if fallback:
return NullTranslations()
raise IOError(ENOENT, 'No translation file found for domain', domain)
# TBD: do we need to worry about the file pointer getting collected?
# Avoid opening, reading, and parsing the .mo file after it's been done
# once.
result = None
for mofile in mofiles:
key = os.path.abspath(mofile)
t = _translations.get(key)
if t is None:
t = _translations.setdefault(key, class_(open(mofile, 'rb')))
# Copy the translation object to allow setting fallbacks.
# All other instance data is shared with the cached object.
t = copy.copy(t)
if result is None:
result = t
else:
result.add_fallback(t)
return result
def install(domain, localedir=None, unicode=False):
translation(domain, localedir, fallback=True).install(unicode)
# a mapping b/w domains and locale directories
_localedirs = {}
# current global domain, `messages' used for compatibility w/ GNU gettext
_current_domain = 'messages'
def textdomain(domain=None):
global _current_domain
if domain is not None:
_current_domain = domain
return _current_domain
def bindtextdomain(domain, localedir=None):
if localedir is not None:
_localedirs[domain] = localedir
return _localedirs.get(domain, _default_localedir)
def dgettext(domain, message):
try:
t = translation(domain, _localedirs.get(domain, None))
except IOError:
return message
return t.gettext(message)
def dngettext(domain, msgid1, msgid2, n):
try:
t = translation(domain, _localedirs.get(domain, None))
except IOError:
if n == 1:
return msgid1
else:
return msgid2
return t.ngettext(msgid1, msgid2, n)
def gettext(message):
return dgettext(_current_domain, message)
def ngettext(msgid1, msgid2, n):
return dngettext(_current_domain, msgid1, msgid2, n)
# dcgettext() has been deemed unnecessary and is not implemented.
# James Henstridge's Catalog constructor from GNOME gettext. Documented usage
# was:
#
# import gettext
# cat = gettext.Catalog(PACKAGE, localedir=LOCALEDIR)
# _ = cat.gettext
# print _('Hello World')
# The resulting catalog object currently don't support access through a
# dictionary API, which was supported (but apparently unused) in GNOME
# gettext.
Catalog = translation