Python locale 模块，lower() 实例源码

def to_locale(language, to_lower=False):
    """
    Turns a language name (en-us) into a locale name (en_US). If 'to_lower' is
    True, the last component is lower-cased (en_us).
    """
    p = language.find('-')
    if p >= 0:
        if to_lower:
            return language[:p].lower()+'_'+language[p+1:].lower()
        else:
            # Get correct locale for sr-latn
            if len(language[p+1:]) > 2:
                return language[:p].lower()+'_'+language[p+1].upper()+language[p+2:].lower()
            return language[:p].lower()+'_'+language[p+1:].upper()
    else:
        return language.lower()

def to_language(locale):
    """Turns a locale name (en_US) into a language name (en-us)."""
    p = locale.find('_')
    if p >= 0:
        return locale[:p].lower()+'-'+locale[p+1:].lower()
    else:
        return locale.lower()

def get_language_from_request(request):
    """
    Analyzes the request to find what language the user wants the system to
    show. Only languages listed in settings.LANGUAGES are taken into account.
    If the user requests a sublanguage where we have a main language, we send
    out the main language.
    """
    global _accepted
    from google.appengine._internal.django.conf import settings
    globalpath = os.path.join(os.path.dirname(sys.modules[settings.__module__].__file__), 'locale')
    supported = dict(settings.LANGUAGES)

    if hasattr(request, 'session'):
        lang_code = request.session.get('django_language', None)
        if lang_code in supported and lang_code is not None and check_for_language(lang_code):
            return lang_code

    lang_code = request.COOKIES.get(settings.LANGUAGE_COOKIE_NAME)

    if lang_code and lang_code not in supported:
        lang_code = lang_code.split('-')[0] # e.g. if fr-ca is not supported fallback to fr

    if lang_code and lang_code in supported and check_for_language(lang_code):
        return lang_code

    accept = request.META.get('HTTP_ACCEPT_LANGUAGE', '')
    for accept_lang, unused in parse_accept_lang_header(accept):
        if accept_lang == '*':
            break

        # We have a very restricted form for our language files (no encoding
        # specifier, since they all must be UTF-8 and only one possible
        # language each time. So we avoid the overhead of gettext.find() and
        # work out the MO file manually.

        # 'normalized' is the root name of the locale in POSIX format (which is
        # the format used for the directories holding the MO files).
        normalized = locale.locale_alias.get(to_locale(accept_lang, True))
        if not normalized:
            continue
        # Remove the default encoding from locale_alias.
        normalized = normalized.split('.')[0]

        if normalized in _accepted:
            # We've seen this locale before and have an MO file for it, so no
            # need to check again.
            return _accepted[normalized]

        for lang, dirname in ((accept_lang, normalized),
                (accept_lang.split('-')[0], normalized.split('_')[0])):
            if lang.lower() not in supported:
                continue
            langfile = os.path.join(globalpath, dirname, 'LC_MESSAGES',
                    'django.mo')
            if os.path.exists(langfile):
                _accepted[normalized] = lang
                return lang

    return settings.LANGUAGE_CODE