"""
flaskext.babel
~~~~~~~~~~~~~~
Implements i18n/l10n support for Flask applications based on Babel.
:copyright: (c) 2013 by Armin Ronacher, Daniel Neuhäuser.
:license: BSD, see LICENSE for more details.
"""
from __future__ import absolute_import
import os
from datetime import datetime
from contextlib import contextmanager
from flask import current_app, request
from flask.ctx import has_request_context
from flask.helpers import locked_cached_property
from babel import dates, numbers, support, Locale
from pytz import timezone, UTC
from werkzeug.datastructures import ImmutableDict
from flask_babel.speaklater import LazyString
[docs]class Babel(object):
"""Central controller class that can be used to configure how
Flask-Babel behaves. Each application that wants to use Flask-Babel
has to create, or run :meth:`init_app` on, an instance of this class
after the configuration was initialized.
"""
default_date_formats = ImmutableDict({
'time': 'medium',
'date': 'medium',
'datetime': 'medium',
'time.short': None,
'time.medium': None,
'time.full': None,
'time.long': None,
'date.short': None,
'date.medium': None,
'date.full': None,
'date.long': None,
'datetime.short': None,
'datetime.medium': None,
'datetime.full': None,
'datetime.long': None,
})
def __init__(self, app=None, default_locale='en', default_timezone='UTC',
default_domain='messages', date_formats=None,
configure_jinja=True):
self._default_locale = default_locale
self._default_timezone = default_timezone
self._default_domain = default_domain
self._date_formats = date_formats
self._configure_jinja = configure_jinja
self.app = app
self.locale_selector_func = None
self.timezone_selector_func = None
if app is not None:
self.init_app(app)
[docs] def init_app(self, app):
"""Set up this instance for use with *app*, if no app was passed to
the constructor.
"""
self.app = app
app.babel_instance = self
if not hasattr(app, 'extensions'):
app.extensions = {}
app.extensions['babel'] = self
app.config.setdefault('BABEL_DEFAULT_LOCALE', self._default_locale)
app.config.setdefault('BABEL_DEFAULT_TIMEZONE', self._default_timezone)
app.config.setdefault('BABEL_DOMAIN', self._default_domain)
if self._date_formats is None:
self._date_formats = self.default_date_formats.copy()
#: a mapping of Babel datetime format strings that can be modified
#: to change the defaults. If you invoke :func:`format_datetime`
#: and do not provide any format string Flask-Babel will do the
#: following things:
#:
#: 1. look up ``date_formats['datetime']``. By default ``'medium'``
#: is returned to enforce medium length datetime formats.
#: 2. ``date_formats['datetime.medium'] (if ``'medium'`` was
#: returned in step one) is looked up. If the return value
#: is anything but `None` this is used as new format string.
#: otherwise the default for that language is used.
self.date_formats = self._date_formats
if self._configure_jinja:
app.jinja_env.filters.update(
datetimeformat=format_datetime,
dateformat=format_date,
timeformat=format_time,
timedeltaformat=format_timedelta,
numberformat=format_number,
decimalformat=format_decimal,
currencyformat=format_currency,
percentformat=format_percent,
scientificformat=format_scientific,
)
app.jinja_env.add_extension('jinja2.ext.i18n')
app.jinja_env.install_gettext_callables(
lambda x: get_translations().ugettext(x),
lambda s, p, n: get_translations().ungettext(s, p, n),
newstyle=True
)
[docs] def localeselector(self, f):
"""Registers a callback function for locale selection. The default
behaves as if a function was registered that returns `None` all the
time. If `None` is returned, the locale falls back to the one from
the configuration.
This has to return the locale as string (eg: ``'de_AT'``, ``'en_US'``)
"""
self.locale_selector_func = f
return f
[docs] def timezoneselector(self, f):
"""Registers a callback function for timezone selection. The default
behaves as if a function was registered that returns `None` all the
time. If `None` is returned, the timezone falls back to the one from
the configuration.
This has to return the timezone as string (eg: ``'Europe/Vienna'``)
"""
self.timezone_selector_func = f
return f
[docs] def list_translations(self):
"""Returns a list of all the locales translations exist for. The
list returned will be filled with actual locale objects and not just
strings.
.. versionadded:: 0.6
"""
result = []
for dirname in self.translation_directories:
if not os.path.isdir(dirname):
continue
for folder in os.listdir(dirname):
locale_dir = os.path.join(dirname, folder, 'LC_MESSAGES')
if not os.path.isdir(locale_dir):
continue
if filter(lambda x: x.endswith('.mo'), os.listdir(locale_dir)):
result.append(Locale.parse(folder))
# If not other translations are found, add the default locale.
if not result:
result.append(Locale.parse(self._default_locale))
return result
@property
def default_locale(self):
"""The default locale from the configuration as instance of a
`babel.Locale` object.
"""
return Locale.parse(self.app.config['BABEL_DEFAULT_LOCALE'])
@property
def default_timezone(self):
"""The default timezone from the configuration as instance of a
`pytz.timezone` object.
"""
return timezone(self.app.config['BABEL_DEFAULT_TIMEZONE'])
@property
def domain(self):
"""The message domain for the translations as a string.
"""
return self.app.config['BABEL_DOMAIN']
[docs] @locked_cached_property
def domain_instance(self):
"""The message domain for the translations.
"""
return Domain(domain=self.app.config['BABEL_DOMAIN'])
@property
def translation_directories(self):
directories = self.app.config.get(
'BABEL_TRANSLATION_DIRECTORIES',
'translations'
).split(';')
for path in directories:
if os.path.isabs(path):
yield path
else:
yield os.path.join(self.app.root_path, path)
[docs]def get_translations():
"""Returns the correct gettext translations that should be used for
this request. This will never fail and return a dummy translation
object if used outside of the request or if a translation cannot be
found.
"""
return get_domain().get_translations()
[docs]def get_locale():
"""Returns the locale that should be used for this request as
`babel.Locale` object. This returns `None` if used outside of
a request.
"""
ctx = _get_current_context()
if ctx is None:
return None
locale = getattr(ctx, 'babel_locale', None)
if locale is None:
babel = current_app.extensions['babel']
if babel.locale_selector_func is None:
locale = babel.default_locale
else:
rv = babel.locale_selector_func()
if rv is None:
locale = babel.default_locale
else:
locale = Locale.parse(rv)
ctx.babel_locale = locale
return locale
[docs]def get_timezone():
"""Returns the timezone that should be used for this request as
`pytz.timezone` object. This returns `None` if used outside of
a request.
"""
ctx = _get_current_context()
tzinfo = getattr(ctx, 'babel_tzinfo', None)
if tzinfo is None:
babel = current_app.extensions['babel']
if babel.timezone_selector_func is None:
tzinfo = babel.default_timezone
else:
rv = babel.timezone_selector_func()
if rv is None:
tzinfo = babel.default_timezone
else:
tzinfo = timezone(rv) if isinstance(rv, str) else rv
ctx.babel_tzinfo = tzinfo
return tzinfo
[docs]def refresh():
"""Refreshes the cached timezones and locale information. This can
be used to switch a translation between a request and if you want
the changes to take place immediately, not just with the next request::
user.timezone = request.form['timezone']
user.locale = request.form['locale']
refresh()
flash(gettext('Language was changed'))
Without that refresh, the :func:`~flask.flash` function would probably
return English text and a now German page.
"""
ctx = _get_current_context()
for key in 'babel_locale', 'babel_tzinfo', 'babel_translations':
if hasattr(ctx, key):
delattr(ctx, key)
if hasattr(ctx, 'forced_babel_locale'):
ctx.babel_locale = ctx.forced_babel_locale
[docs]@contextmanager
def force_locale(locale):
"""Temporarily overrides the currently selected locale.
Sometimes it is useful to switch the current locale to different one, do
some tasks and then revert back to the original one. For example, if the
user uses German on the web site, but you want to send them an email in
English, you can use this function as a context manager::
with force_locale('en_US'):
send_email(gettext('Hello!'), ...)
:param locale: The locale to temporary switch to (ex: 'en_US').
"""
ctx = _get_current_context()
if ctx is None:
yield
return
orig_attrs = {}
for key in ('babel_translations', 'babel_locale'):
orig_attrs[key] = getattr(ctx, key, None)
try:
ctx.babel_locale = Locale.parse(locale)
ctx.forced_babel_locale = ctx.babel_locale
ctx.babel_translations = None
yield
finally:
if hasattr(ctx, 'forced_babel_locale'):
del ctx.forced_babel_locale
for key, value in orig_attrs.items():
setattr(ctx, key, value)
def _get_format(key, format):
"""A small helper for the datetime formatting functions. Looks up
format defaults for different kinds.
"""
babel = current_app.extensions['babel']
if format is None:
format = babel.date_formats[key]
if format in ('short', 'medium', 'full', 'long'):
rv = babel.date_formats['%s.%s' % (key, format)]
if rv is not None:
format = rv
return format
[docs]def to_user_timezone(datetime):
"""Convert a datetime object to the user's timezone. This automatically
happens on all date formatting unless rebasing is disabled. If you need
to convert a :class:`datetime.datetime` object at any time to the user's
timezone (as returned by :func:`get_timezone` this function can be used).
"""
if datetime.tzinfo is None:
datetime = datetime.replace(tzinfo=UTC)
tzinfo = get_timezone()
return tzinfo.normalize(datetime.astimezone(tzinfo))
[docs]def to_utc(datetime):
"""Convert a datetime object to UTC and drop tzinfo. This is the
opposite operation to :func:`to_user_timezone`.
"""
if datetime.tzinfo is None:
datetime = get_timezone().localize(datetime)
return datetime.astimezone(UTC).replace(tzinfo=None)
def _date_format(formatter, obj, format, rebase, **extra):
"""Internal helper that formats the date."""
locale = get_locale()
extra = {}
if formatter is not dates.format_date and rebase:
extra['tzinfo'] = get_timezone()
return formatter(obj, format, locale=locale, **extra)
class Domain(object):
"""Localization domain. By default will use look for tranlations in Flask
application directory and "messages" domain - all message catalogs should
be called ``messages.mo``.
"""
def __init__(self, translation_directories=None, domain='messages'):
if isinstance(translation_directories, str):
translation_directories = [translation_directories]
self._translation_directories = translation_directories
self.domain = domain
self.cache = {}
def __repr__(self):
return '<Domain({!r}, {!r})>'.format(self._translation_directories, self.domain)
@property
def translation_directories(self):
if self._translation_directories is not None:
return self._translation_directories
babel = current_app.extensions['babel']
return babel.translation_directories
def as_default(self):
"""Set this domain as default for the current request"""
ctx = _get_current_context()
if ctx is None:
raise RuntimeError("No request context")
ctx.babel_domain = self
def get_translations_cache(self, ctx):
"""Returns dictionary-like object for translation caching"""
return self.cache
def get_translations(self):
ctx = _get_current_context()
if ctx is None:
return support.NullTranslations()
cache = self.get_translations_cache(ctx)
locale = get_locale()
try:
return cache[str(locale), self.domain]
except KeyError:
translations = support.Translations()
for dirname in self.translation_directories:
catalog = support.Translations.load(
dirname,
[locale],
self.domain
)
translations.merge(catalog)
# FIXME: Workaround for merge() being really, really stupid. It
# does not copy _info, plural(), or any other instance variables
# populated by GNUTranslations. We probably want to stop using
# `support.Translations.merge` entirely.
if hasattr(catalog, 'plural'):
translations.plural = catalog.plural
cache[str(locale), self.domain] = translations
return translations
def gettext(self, string, **variables):
"""Translates a string with the current locale and passes in the
given keyword arguments as mapping to a string formatting string.
::
gettext(u'Hello World!')
gettext(u'Hello %(name)s!', name='World')
"""
t = self.get_translations()
s = t.ugettext(string)
return s if not variables else s % variables
def ngettext(self, singular, plural, num, **variables):
"""Translates a string with the current locale and passes in the
given keyword arguments as mapping to a string formatting string.
The `num` parameter is used to dispatch between singular and various
plural forms of the message. It is available in the format string
as ``%(num)d`` or ``%(num)s``. The source language should be
English or a similar language which only has one plural form.
::
ngettext(u'%(num)d Apple', u'%(num)d Apples', num=len(apples))
"""
variables.setdefault('num', num)
t = self.get_translations()
s = t.ungettext(singular, plural, num)
return s if not variables else s % variables
def pgettext(self, context, string, **variables):
"""Like :func:`gettext` but with a context.
.. versionadded:: 0.7
"""
t = self.get_translations()
s = t.upgettext(context, string)
return s if not variables else s % variables
def npgettext(self, context, singular, plural, num, **variables):
"""Like :func:`ngettext` but with a context.
.. versionadded:: 0.7
"""
variables.setdefault('num', num)
t = self.get_translations()
s = t.unpgettext(context, singular, plural, num)
return s if not variables else s % variables
def lazy_gettext(self, string, **variables):
"""Like :func:`gettext` but the string returned is lazy which means
it will be translated when it is used as an actual string.
Example::
hello = lazy_gettext(u'Hello World')
@app.route('/')
def index():
return unicode(hello)
"""
return LazyString(self.gettext, string, **variables)
def lazy_ngettext(self, singular, plural, num, **variables):
"""Like :func:`ngettext` but the string returned is lazy which means
it will be translated when it is used as an actual string.
Example::
apples = lazy_ngettext(u'%(num)d Apple', u'%(num)d Apples', num=len(apples))
@app.route('/')
def index():
return unicode(apples)
"""
return LazyString(self.ngettext, singular, plural, num, **variables)
def lazy_pgettext(self, context, string, **variables):
"""Like :func:`pgettext` but the string returned is lazy which means
it will be translated when it is used as an actual string.
.. versionadded:: 0.7
"""
return LazyString(self.pgettext, context, string, **variables)
def _get_current_context():
if has_request_context():
return request
if current_app:
return current_app
def get_domain():
ctx = _get_current_context()
if ctx is None:
# this will use NullTranslations
return Domain()
try:
return ctx.babel_domain
except AttributeError:
pass
babel = current_app.extensions['babel']
ctx.babel_domain = babel.domain_instance
return ctx.babel_domain
# Create shortcuts for the default Flask domain
[docs]def gettext(*args, **kwargs):
return get_domain().gettext(*args, **kwargs)
_ = gettext
[docs]def ngettext(*args, **kwargs):
return get_domain().ngettext(*args, **kwargs)
[docs]def pgettext(*args, **kwargs):
return get_domain().pgettext(*args, **kwargs)
[docs]def npgettext(*args, **kwargs):
return get_domain().npgettext(*args, **kwargs)
[docs]def lazy_gettext(*args, **kwargs):
return LazyString(gettext, *args, **kwargs)
[docs]def lazy_pgettext(*args, **kwargs):
return LazyString(pgettext, *args, **kwargs)
def lazy_ngettext(*args, **kwargs):
return LazyString(ngettext, *args, **kwargs)