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151 | import datetime
import warnings
import pytz
from django.conf import settings
from django.db import models
from django.dispatch import dispatcher
from django.db.models import signals
try:
pytz_exc = (pytz.UnknownTimeZoneError,)
except AttributeError:
# older versions of pytz
pytz_exc = (IOError, KeyError)
TIMEZONES = tuple((t, t) for t in pytz.all_timezones)
class UTCDateTimeField(models.DateTimeField):
def __init__(self, *args, **kw):
self.default_tz = kw.get('default_tz')
if 'default_tz' in kw:
del(kw['default_tz'])
super(UTCDateTimeField, self).__init__(*args, **kw)
self._name = None
def get_internal_type(self):
return 'DateTimeField'
def _model_init(self, signal, sender, instance, **kw):
setattr(instance, "_%s" % self._name, getattr(instance, self._name))
setattr(instance, "_%s_utc" % self._name, getattr(instance, "%s_utc" % self._name))
setattr(instance, "_%s_tz" % self._name, getattr(instance, "%s_tz" % self._name))
def _model_pre_save(self, signal, sender, instance, **kw):
dt = getattr(instance, self._name)
utc = getattr(instance, "%s_utc" % self._name)
tz = getattr(instance, "%s_tz" % self._name)
if not tz:
# try to get the default
if isinstance(self.default_tz, basestring):
tz = getattr(instance, self.default_tz)
if isinstance(tz, basestring):
# use it as a timezone
pass
elif callable(tz):
self.default_tz = tz
tz = None
else:
warnings.warn("UTCDateTimeField cannot use default_tz %s in model %s" % (self.default_tz, instance))
self.default_tz = lambda: getattr(settings, 'TIME_ZONE', 'UTC')
tz = None
if callable(self.default_tz):
tz = self.default_tz()
if not tz or not isinstance(tz, basestring):
warnings.warn("UTCDateTimeField cannot use default timezone %s, using Django default" % tz)
tz = getattr(settings, 'TIME_ZONE', 'UTC')
if not tz:
tz = getattr(settings, 'TIME_ZONE', 'UTC')
setattr(instance, "%s_tz" % self._name, tz)
_dt = getattr(instance, "_%s" % self._name)
_utc = getattr(instance, "_%s_utc" % self._name)
_tz = getattr(instance, "_%s_tz" % self._name)
if isinstance(tz, unicode):
tz = tz.encode('utf8')
try:
timezone = pytz.timezone(tz)
except pytz_exc, e:
warnings.warn("Error in timezone: %s" % e)
setattr(instance, "%s_tz" % self._name, 'UTC')
timezone = pytz.UTC
if not dt and not utc:
# do nothing
return
elif dt and dt != _dt:
utc = UTCDateTimeField.utc_from_localtime(dt, timezone)
setattr(instance, "%s_utc" % self._name, utc)
elif utc and (utc != _utc or tz != _tz):
dt = UTCDateTimeField.localtime_from_utc(utc, timezone)
setattr(instance, "_%s" % self._name, dt)
elif not dt:
dt = UTCDateTimeField.localtime_from_utc(utc, timezone)
setattr(instance, "_%s" % self._name, dt)
elif not utc:
utc = UTCDateTimeField.utc_from_localtime(dt, timezone)
setattr(instance, "%s_utc" % self._name, utc)
if dt.tzinfo:
dt = dt.replace(tzinfo=None)
if utc.tzinfo:
utc = utc.replace(tzinfo=None)
setattr(instance, "_%s" % self._name, dt)
setattr(instance, "_%s_utc" % self._name, utc)
setattr(instance, "_%s_tz" % self._name, tz)
setattr(instance, "%s" % self._name, dt)
setattr(instance, "%s_utc" % self._name, utc)
def _model_post_save(self, signal, sender, instance, **kw):
setattr(instance, "%s" % self._name, getattr(instance, "_%s" % self._name))
setattr(instance, "%s_utc" % self._name, getattr(instance, "_%s_utc" % self._name))
def contribute_to_class(self, cls, name):
self._name = name
super(UTCDateTimeField, self).contribute_to_class(cls, name)
self.utc_field = models.DateTimeField(blank=True)
self.creation_counter = self.utc_field.creation_counter + 1
models.DateTimeField.contribute_to_class(self.utc_field, cls, '%s_utc' % name)
self.tz_field = models.CharField(max_length=38, blank=True, choices=TIMEZONES, default=getattr(settings, 'TIME_ZONE', 'UTC'))
self.creation_counter = self.tz_field.creation_counter + 1
models.CharField.contribute_to_class(self.tz_field, cls, '%s_tz' % name)
# add the properties for offset-aware datetimes
def get_timezone(s):
tz = getattr(s, '%s_tz' % name)
if isinstance(tz, unicode):
tz = tz.encode('utf8')
return pytz.timezone(tz)
setattr(cls, "%s_timezone" % name, property(get_timezone))
def get_dt_offset_aware(s):
dt = getattr(s, "%s_utc_offset_aware" % name)
tz = getattr(s, "%s_timezone" % name)
return dt.astimezone(tz)
setattr(cls, "%s_offset_aware" % name, property(get_dt_offset_aware))
def get_utc_offset_aware(s):
return getattr(s, '%s_utc' % name).replace(tzinfo=pytz.utc)
setattr(cls, "%s_utc_offset_aware" % name, property(get_utc_offset_aware))
signals.post_init.connect(self._model_init, sender=cls)
signals.pre_save.connect(self._model_pre_save, sender=cls)
signals.post_save.connect(self._model_post_save, sender=cls)
@staticmethod
def localtime_from_utc(utc, tz):
dt = utc.replace(tzinfo=pytz.utc)
return dt.astimezone(tz)
@staticmethod
def utc_from_localtime(dt, tz):
dt = dt.replace(tzinfo=tz)
_dt = tz.normalize(dt)
if dt.tzinfo != _dt.tzinfo:
# Houston, we have a problem...
# find out which one has a dst offset
if _dt.tzinfo.dst(_dt):
_dt -= _dt.tzinfo.dst(_dt)
else:
_dt += dt.tzinfo.dst(dt)
return _dt.astimezone(pytz.utc)
|
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Comments
Anyone have a solution for a UTCTimeField()? I need similar functionality but only need the time portion. I guess I could use this snippet but ignore whatever date is there.
However, it seems this snippet is broken in Changeset 8223. The dispatcher functionality has been replaced with the new django.dispatch.Signal:
http://code.djangoproject.com/wiki/BackwardsIncompatibleChanges#Signalrefactoring
I'm currently struggling to fix this but I'm still a beginner when it comes to all the custom fields, dispatching and signal jazz. Any help would be appreciated.
#
Updated to work with Django 1.1+ (I use it with trunk == 1.2)
#
You mean this code can be used with Django 1.1+?
#
I don't know about others but the
staticmethodutc_from_localtimewas off for timezones like 'Europe/Paris'. So after a quick Google search I found this threadThe following code is based on the original version of the method. You can see that the returned value is the the current Paris time minus 9 minutes. Just weird, probably because the localize function has not been called. It should be a -1 hour offset, not -9 min.
#