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190 | from datetime import datetime, tzinfo
import pytz
from django.template import Library, Node, TemplateSyntaxError
from django.utils import timezone
register = Library()
# HACK: datetime instances cannot be assigned new attributes. Define a subclass
# in order to define new attributes in do_timezone().
class datetimeobject(datetime):
pass
# Template filters
@register.filter
def localtime(value):
"""
Convert a datetime to local time in the active time zone.
This only makes sense within a {% localtime off %} block.
"""
return do_timezone(value, timezone.get_current_timezone())
@register.filter
def utc(value):
"""
Convert a datetime to UTC.
"""
return do_timezone(value, timezone.utc)
@register.filter('timezone')
def do_timezone(value, arg):
"""
Convert a datetime to local time in a given time zone.
The argument must be an instance of a tzinfo subclass or a time zone name.
Naive datetimes are assumed to be in local time in the default time zone.
"""
if not isinstance(value, datetime):
return ''
# Obtain a timezone-aware datetime
try:
if timezone.is_naive(value):
default_timezone = timezone.get_default_timezone()
value = timezone.make_aware(value, default_timezone)
# Filters must never raise exceptions, and pytz' exceptions inherit
# Exception directly, not a specific subclass. So catch everything.
except Exception:
return ''
# Obtain a tzinfo instance
if isinstance(arg, tzinfo):
tz = arg
elif isinstance(arg, str):
try:
tz = pytz.timezone(arg)
except pytz.UnknownTimeZoneError:
return ''
else:
return ''
result = timezone.localtime(value, tz)
# HACK: the convert_to_local_time flag will prevent
# automatic conversion of the value to local time.
result = datetimeobject(result.year, result.month, result.day,
result.hour, result.minute, result.second,
result.microsecond, result.tzinfo)
result.convert_to_local_time = False
return result
# Template tags
class LocalTimeNode(Node):
"""
Template node class used by ``localtime_tag``.
"""
def __init__(self, nodelist, use_tz):
self.nodelist = nodelist
self.use_tz = use_tz
def render(self, context):
old_setting = context.use_tz
context.use_tz = self.use_tz
output = self.nodelist.render(context)
context.use_tz = old_setting
return output
class TimezoneNode(Node):
"""
Template node class used by ``timezone_tag``.
"""
def __init__(self, nodelist, tz):
self.nodelist = nodelist
self.tz = tz
def render(self, context):
with timezone.override(self.tz.resolve(context)):
output = self.nodelist.render(context)
return output
class GetCurrentTimezoneNode(Node):
"""
Template node class used by ``get_current_timezone_tag``.
"""
def __init__(self, variable):
self.variable = variable
def render(self, context):
context[self.variable] = timezone.get_current_timezone_name()
return ''
@register.tag('localtime')
def localtime_tag(parser, token):
"""
Force or prevent conversion of datetime objects to local time,
regardless of the value of ``settings.USE_TZ``.
Sample usage::
{% localtime off %}{{ value_in_utc }}{% endlocaltime %}
"""
bits = token.split_contents()
if len(bits) == 1:
use_tz = True
elif len(bits) > 2 or bits[1] not in ('on', 'off'):
raise TemplateSyntaxError("%r argument should be 'on' or 'off'" %
bits[0])
else:
use_tz = bits[1] == 'on'
nodelist = parser.parse(('endlocaltime',))
parser.delete_first_token()
return LocalTimeNode(nodelist, use_tz)
@register.tag('timezone')
def timezone_tag(parser, token):
"""
Enable a given time zone just for this block.
The ``timezone`` argument must be an instance of a ``tzinfo`` subclass, a
time zone name, or ``None``. If it is ``None``, the default time zone is
used within the block.
Sample usage::
{% timezone "Europe/Paris" %}
It is {{ now }} in Paris.
{% endtimezone %}
"""
bits = token.split_contents()
if len(bits) != 2:
raise TemplateSyntaxError("'%s' takes one argument (timezone)" %
bits[0])
tz = parser.compile_filter(bits[1])
nodelist = parser.parse(('endtimezone',))
parser.delete_first_token()
return TimezoneNode(nodelist, tz)
@register.tag("get_current_timezone")
def get_current_timezone_tag(parser, token):
"""
Store the name of the current time zone in the context.
Usage::
{% get_current_timezone as TIME_ZONE %}
This will fetch the currently active time zone and put its name
into the ``TIME_ZONE`` context variable.
"""
# token.split_contents() isn't useful here because this tag doesn't accept variable as arguments
args = token.contents.split()
if len(args) != 3 or args[1] != 'as':
raise TemplateSyntaxError("'get_current_timezone' requires "
"'as variable' (got %r)" % args)
return GetCurrentTimezoneNode(args[2])
|