Source code for gettext

"""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 locale, copy, io, 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.base_prefix, 'share', 'locale')


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
    import token, tokenize
    tokens = tokenize.generate_tokens(io.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 "b if a else c".
    expr = re.compile(r'(.*?)\?(.*?):(.*)')
    def repl(x):
        return "(%s if %s else %s)" % (x.group(2), x.group(1),
                                       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(loc):
    loc = locale.normalize(loc)
    COMPONENT_CODESET   = 1 << 0
    COMPONENT_TERRITORY = 1 << 1
    COMPONENT_MODIFIER  = 1 << 2
    # split up the locale into its base components
    mask = 0
    pos = loc.find('@')
    if pos >= 0:
        modifier = loc[pos:]
        loc = loc[:pos]
        mask |= COMPONENT_MODIFIER
    else:
        modifier = ''
    pos = loc.find('.')
    if pos >= 0:
        codeset = loc[pos:]
        loc = loc[:pos]
        mask |= COMPONENT_CODESET
    else:
        codeset = ''
    pos = loc.find('_')
    if pos >= 0:
        territory = loc[pos:]
        loc = loc[:pos]
        mask |= COMPONENT_TERRITORY
    else:
        territory = ''
    language = loc
    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



[docs]class NullTranslations: def __init__(self, fp=None): self._info = {} self._charset = None self._output_charset = None self._fallback = None if fp is not None: self._parse(fp)
[docs] def _parse(self, fp): pass
[docs] def add_fallback(self, fallback): if self._fallback: self._fallback.add_fallback(fallback) else: self._fallback = fallback
[docs] def gettext(self, message): if self._fallback: return self._fallback.gettext(message) return message
[docs] def lgettext(self, message): if self._fallback: return self._fallback.lgettext(message) return message
[docs] def ngettext(self, msgid1, msgid2, n): if self._fallback: return self._fallback.ngettext(msgid1, msgid2, n) if n == 1: return msgid1 else: return msgid2
[docs] def lngettext(self, msgid1, msgid2, n): if self._fallback: return self._fallback.lngettext(msgid1, msgid2, n) if n == 1: return msgid1 else: return msgid2
[docs] def info(self): return self._info
[docs] def charset(self): return self._charset
[docs] def output_charset(self): return self._output_charset
[docs] def set_output_charset(self, charset): self._output_charset = charset
[docs] def install(self, names=None): import builtins builtins.__dict__['_'] = self.gettext if hasattr(names, "__contains__"): if "gettext" in names: builtins.__dict__['gettext'] = builtins.__dict__['_'] if "ngettext" in names: builtins.__dict__['ngettext'] = self.ngettext if "lgettext" in names: builtins.__dict__['lgettext'] = self.lgettext if "lngettext" in names: builtins.__dict__['lngettext'] = self.lngettext
class GNUTranslations(NullTranslations): # Magic number of .mo files LE_MAGIC = 0x950412de BE_MAGIC = 0xde120495 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 OSError(0, 'Bad magic number', filename) # Now put all messages from the .mo file buffer into the catalog # dictionary. for i in range(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 OSError(0, 'File is corrupt', filename) # See if we're looking at GNU .mo conventions for metadata if mlen == 0: # Catalog description lastk = k = None for b_item in tmsg.split('\n'.encode("ascii")): item = b_item.decode().strip() if not item: continue if ':' in item: k, v = item.split(':', 1) k = k.strip().lower() v = v.strip() self._info[k] = v lastk = k elif lastk: self._info[lastk] += '\n' + item 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 applications # 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. charset = self._charset or 'ascii' if b'\x00' in msg: # Plural forms msgid1, msgid2 = msg.split(b'\x00') tmsg = tmsg.split(b'\x00') msgid1 = str(msgid1, charset) for i, x in enumerate(tmsg): catalog[(msgid1, i)] = str(x, charset) else: catalog[str(msg, charset)] = str(tmsg, charset) # advance to next entry in the seek tables masteridx += 8 transidx += 8
[docs] def lgettext(self, message): missing = object() tmsg = self._catalog.get(message, missing) if tmsg is missing: if self._fallback: return self._fallback.lgettext(message) return message if self._output_charset: return tmsg.encode(self._output_charset) return tmsg.encode(locale.getpreferredencoding())
[docs] def lngettext(self, msgid1, msgid2, n): try: tmsg = self._catalog[(msgid1, self.plural(n))] if self._output_charset: return tmsg.encode(self._output_charset) return tmsg.encode(locale.getpreferredencoding()) except KeyError: if self._fallback: return self._fallback.lngettext(msgid1, msgid2, n) if n == 1: return msgid1 else: return msgid2
[docs] 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 return tmsg
[docs] def ngettext(self, msgid1, msgid2, n): try: tmsg = self._catalog[(msgid1, self.plural(n))] except KeyError: if self._fallback: return self._fallback.ngettext(msgid1, msgid2, n) if n == 1: tmsg = msgid1 else: tmsg = msgid2 return tmsg # Locate a .mo file using the gettext strategy
[docs]def find(domain, localedir=None, languages=None, all=False): # 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 = {}
[docs]def translation(domain, localedir=None, languages=None, class_=None, fallback=False, codeset=None): if class_ is None: class_ = GNUTranslations mofiles = find(domain, localedir, languages, all=True) if not mofiles: if fallback: return NullTranslations() raise OSError(ENOENT, 'No translation file found for domain', domain) # Avoid opening, reading, and parsing the .mo file after it's been done # once. result = None for mofile in mofiles: key = (class_, os.path.abspath(mofile)) t = _translations.get(key) if t is None: with open(mofile, 'rb') as fp: t = _translations.setdefault(key, class_(fp)) # Copy the translation object to allow setting fallbacks and # output charset. All other instance data is shared with the # cached object. t = copy.copy(t) if codeset: t.set_output_charset(codeset) if result is None: result = t else: result.add_fallback(t) return result
[docs]def install(domain, localedir=None, codeset=None, names=None): t = translation(domain, localedir, fallback=True, codeset=codeset) t.install(names) # a mapping b/w domains and locale directories
_localedirs = {} # a mapping b/w domains and codesets _localecodesets = {} # current global domain, `messages' used for compatibility w/ GNU gettext _current_domain = 'messages'
[docs]def textdomain(domain=None): global _current_domain if domain is not None: _current_domain = domain return _current_domain
[docs]def bindtextdomain(domain, localedir=None): global _localedirs if localedir is not None: _localedirs[domain] = localedir return _localedirs.get(domain, _default_localedir)
[docs]def bind_textdomain_codeset(domain, codeset=None): global _localecodesets if codeset is not None: _localecodesets[domain] = codeset return _localecodesets.get(domain)
[docs]def dgettext(domain, message): try: t = translation(domain, _localedirs.get(domain, None), codeset=_localecodesets.get(domain)) except OSError: return message return t.gettext(message)
[docs]def ldgettext(domain, message): try: t = translation(domain, _localedirs.get(domain, None), codeset=_localecodesets.get(domain)) except OSError: return message return t.lgettext(message)
[docs]def dngettext(domain, msgid1, msgid2, n): try: t = translation(domain, _localedirs.get(domain, None), codeset=_localecodesets.get(domain)) except OSError: if n == 1: return msgid1 else: return msgid2 return t.ngettext(msgid1, msgid2, n)
[docs]def ldngettext(domain, msgid1, msgid2, n): try: t = translation(domain, _localedirs.get(domain, None), codeset=_localecodesets.get(domain)) except OSError: if n == 1: return msgid1 else: return msgid2 return t.lngettext(msgid1, msgid2, n)
[docs]def gettext(message): return dgettext(_current_domain, message)
[docs]def lgettext(message): return ldgettext(_current_domain, message)
[docs]def ngettext(msgid1, msgid2, n): return dngettext(_current_domain, msgid1, msgid2, n)
[docs]def lngettext(msgid1, msgid2, n): return ldngettext(_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