# Django 2.2.9.dev20191202104323 文档

# django.utils.translation 源代码

    """
    Internationalization support.
    """
    import re
    from contextlib import ContextDecorator

    from django.utils.autoreload import autoreload_started, file_changed
    from django.utils.functional import lazy

    __all__ = [
        'activate', 'deactivate', 'override', 'deactivate_all',
        'get_language', 'get_language_from_request',
        'get_language_info', 'get_language_bidi',
        'check_for_language', 'to_language', 'to_locale', 'templatize',
        'gettext', 'gettext_lazy', 'gettext_noop',
        'ugettext', 'ugettext_lazy', 'ugettext_noop',
        'ngettext', 'ngettext_lazy',
        'ungettext', 'ungettext_lazy',
        'pgettext', 'pgettext_lazy',
        'npgettext', 'npgettext_lazy',
        'LANGUAGE_SESSION_KEY',
    ]

    LANGUAGE_SESSION_KEY = '_language'

    class TranslatorCommentWarning(SyntaxWarning):
        pass

    # Here be dragons, so a short explanation of the logic won't hurt:
    # We are trying to solve two problems: (1) access settings, in particular
    # settings.USE_I18N, as late as possible, so that modules can be imported
    # without having to first configure Django, and (2) if some other code creates
    # a reference to one of these functions, don't break that reference when we
    # replace the functions with their real counterparts (once we do access the
    # settings).

    class Trans:
        """
        The purpose of this class is to store the actual translation function upon
        receiving the first call to that function. After this is done, changes to
        USE_I18N will have no effect to which function is served upon request. If
        your tests rely on changing USE_I18N, you can delete all the functions
        from _trans.__dict__.

        Note that storing the function with setattr will have a noticeable
        performance effect, as access to the function goes the normal path,
        instead of using __getattr__.
        """

        def __getattr__(self, real_name):
            from django.conf import settings
            if settings.USE_I18N:
                from django.utils.translation import trans_real as trans
                from django.utils.translation.reloader import watch_for_translation_changes, translation_file_changed
                autoreload_started.connect(watch_for_translation_changes, dispatch_uid='translation_file_changed')
                file_changed.connect(translation_file_changed, dispatch_uid='translation_file_changed')
            else:
                from django.utils.translation import trans_null as trans
            setattr(self, real_name, getattr(trans, real_name))
            return getattr(trans, real_name)

    _trans = Trans()

    # The Trans class is no more needed, so remove it from the namespace.
    del Trans

    def gettext_noop(message):
        return _trans.gettext_noop(message)

    ugettext_noop = gettext_noop

    def gettext(message):
        return _trans.gettext(message)

    # An alias since Django 2.0
    ugettext = gettext

    def ngettext(singular, plural, number):
        return _trans.ngettext(singular, plural, number)

    # An alias since Django 2.0
    ungettext = ngettext

    def pgettext(context, message):
        return _trans.pgettext(context, message)

    def npgettext(context, singular, plural, number):
        return _trans.npgettext(context, singular, plural, number)

    gettext_lazy = ugettext_lazy = lazy(gettext, str)
    pgettext_lazy = lazy(pgettext, str)

    def lazy_number(func, resultclass, number=None, **kwargs):
        if isinstance(number, int):
            kwargs['number'] = number
            proxy = lazy(func, resultclass)(**kwargs)
        else:
            original_kwargs = kwargs.copy()

            class NumberAwareString(resultclass):
                def __bool__(self):
                    return bool(kwargs['singular'])

                def _get_number_value(self, values):
                    try:
                        return values[number]
                    except KeyError:
                        raise KeyError(
                            "Your dictionary lacks key '%s\'. Please provide "
                            "it, because it is required to determine whether "
                            "string is singular or plural." % number
                        )

                def _translate(self, number_value):
                    kwargs['number'] = number_value
                    return func(**kwargs)

                def format(self, *args, **kwargs):
                    number_value = self._get_number_value(kwargs) if kwargs and number else args[0]
                    return self._translate(number_value).format(*args, **kwargs)

                def __mod__(self, rhs):
                    if isinstance(rhs, dict) and number:
                        number_value = self._get_number_value(rhs)
                    else:
                        number_value = rhs
                    translated = self._translate(number_value)
                    try:
                        translated = translated % rhs
                    except TypeError:
                        # String doesn't contain a placeholder for the number.
                        pass
                    return translated

            proxy = lazy(lambda **kwargs: NumberAwareString(), NumberAwareString)(**kwargs)
            proxy.__reduce__ = lambda: (_lazy_number_unpickle, (func, resultclass, number, original_kwargs))
        return proxy

    def _lazy_number_unpickle(func, resultclass, number, kwargs):
        return lazy_number(func, resultclass, number=number, **kwargs)

    def ngettext_lazy(singular, plural, number=None):
        return lazy_number(ngettext, str, singular=singular, plural=plural, number=number)

    # An alias since Django 2.0
    ungettext_lazy = ngettext_lazy

    def npgettext_lazy(context, singular, plural, number=None):
        return lazy_number(npgettext, str, context=context, singular=singular, plural=plural, number=number)

    def activate(language):
        return _trans.activate(language)

    def deactivate():
        return _trans.deactivate()

    class override(ContextDecorator):
        def __init__(self, language, deactivate=False):
            self.language = language
            self.deactivate = deactivate

        def __enter__(self):
            self.old_language = get_language()
            if self.language is not None:
                activate(self.language)
            else:
                deactivate_all()

        def __exit__(self, exc_type, exc_value, traceback):
            if self.old_language is None:
                deactivate_all()
            elif self.deactivate:
                deactivate()
            else:
                activate(self.old_language)

    def get_language():
        return _trans.get_language()

    def get_language_bidi():
        return _trans.get_language_bidi()

    def check_for_language(lang_code):
        return _trans.check_for_language(lang_code)

    def to_language(locale):
        """Turn 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 to_locale(language):
        """Turn a language name (en-us) into a locale name (en_US)."""
        language, _, country = language.lower().partition('-')
        if not country:
            return language
        # A language with > 2 characters after the dash only has its first
        # character after the dash capitalized; e.g. sr-latn becomes sr_Latn.
        # A language with 2 characters after the dash has both characters
        # capitalized; e.g. en-us becomes en_US.
        country, _, tail = country.partition('-')
        country = country.title() if len(country) > 2 else country.upper()
        if tail:
            country += '-' + tail
        return language + '_' + country

    def get_language_from_request(request, check_path=False):
        return _trans.get_language_from_request(request, check_path)

    def get_language_from_path(path):
        return _trans.get_language_from_path(path)

    def get_supported_language_variant(lang_code, *, strict=False):
        return _trans.get_supported_language_variant(lang_code, strict)

    def templatize(src, **kwargs):
        from .template import templatize
        return templatize(src, **kwargs)

    def deactivate_all():
        return _trans.deactivate_all()

    def get_language_info(lang_code):
        from django.conf.locale import LANG_INFO
        try:
            lang_info = LANG_INFO[lang_code]
            if 'fallback' in lang_info and 'name' not in lang_info:
                info = get_language_info(lang_info['fallback'][0])
            else:
                info = lang_info
        except KeyError:
            if '-' not in lang_code:
                raise KeyError("Unknown language code %s." % lang_code)
            generic_lang_code = lang_code.split('-')[0]
            try:
                info = LANG_INFO[generic_lang_code]
            except KeyError:
                raise KeyError("Unknown language code %s and %s." % (lang_code, generic_lang_code))

        if info:
            info['name_translated'] = gettext_lazy(info['name'])
        return info

    trim_whitespace_re = re.compile(r'\s*\n\s*')

    def trim_whitespace(s):
        return trim_whitespace_re.sub(' ', s.strip())