Used datetime.timezone.utc instead of pytz.utc for better performance.

django/contrib/sessions/backends/file.py

@@ -59,10 +59,7 @@ def _last_modification(self):
  Return the modification time of the file storing the session's content.
  """
  modification = os.stat(self._key_to_file()).st_mtime
- if settings.USE_TZ:
- modification = datetime.datetime.utcfromtimestamp(modification)
- return modification.replace(tzinfo=timezone.utc)
- return datetime.datetime.fromtimestamp(modification)
+ return datetime.datetime.fromtimestamp(modification, timezone.utc if settings.USE_TZ else None)
 
  def _expiry_date(self, session_data):
  """

django/core/files/storage.py

@@ -336,11 +336,7 @@ def _datetime_from_timestamp(self, ts):
  If timezone support is enabled, make an aware datetime object in UTC;
  otherwise make a naive one in the local timezone.
  """
- if settings.USE_TZ:
- # Safe to use .replace() because UTC doesn't have DST
- return datetime.utcfromtimestamp(ts).replace(tzinfo=timezone.utc)
- else:
- return datetime.fromtimestamp(ts)
+ return datetime.fromtimestamp(ts, timezone.utc if settings.USE_TZ else None)
 
  def get_accessed_time(self, name):
  return self._datetime_from_timestamp(os.path.getatime(self.path(name)))

django/db/migrations/serializer.py

@@ -50,7 +50,7 @@ class DatetimeSerializer(BaseSerializer):
  def serialize(self):
  if self.value.tzinfo is not None and self.value.tzinfo != utc:
  self.value = self.value.astimezone(utc)
- value_repr = repr(self.value).replace("<UTC>", "utc")
+ value_repr = repr(self.value).replace("datetime.timezone(datetime.timedelta(0), 'UTC')", 'utc')
  if isinstance(self.value, datetime_safe.datetime):
  value_repr = "datetime.%s" % value_repr
  imports = ["import datetime"]

django/utils/feedgenerator.py

@@ -173,8 +173,7 @@ def latest_post_date(self):
  if latest_date is None or item_date > latest_date:
  latest_date = item_date
 
- # datetime.now(tz=utc) is slower, as documented in django.utils.timezone.now
- return latest_date or datetime.datetime.utcnow().replace(tzinfo=utc)
+ return latest_date or datetime.datetime.now(utc)
 
 
 class Enclosure:

django/utils/timezone.py

@@ -2,9 +2,10 @@
 Timezone-related classes and functions.
 """
 
+import datetime
 import functools
 from contextlib import ContextDecorator
-from datetime import datetime, timedelta, tzinfo
+from datetime import timedelta, tzinfo
 from threading import local
 
 import pytz
@@ -52,7 +53,8 @@ def dst(self, dt):
 
 
 # UTC time zone as a tzinfo instance.
-utc = pytz.utc
+# (Use utc = datetime.timezone.utc here when PY35 isn't supported.)
+utc = datetime.timezone(ZERO, 'UTC')
 
 
 def get_fixed_timezone(offset):
@@ -172,7 +174,7 @@ def template_localtime(value, use_tz=None):
  This function is designed for use by the template engine.
  """
  should_convert = (
- isinstance(value, datetime) and
+ isinstance(value, datetime.datetime) and
  (settings.USE_TZ if use_tz is None else use_tz) and
  not is_naive(value) and
  getattr(value, 'convert_to_local_time', True)
@@ -219,11 +221,7 @@ def now():
  """
  Return an aware or naive datetime.datetime, depending on settings.USE_TZ.
  """
- if settings.USE_TZ:
- # timeit shows that datetime.now(tz=utc) is 24% slower
- return datetime.utcnow().replace(tzinfo=utc)
- else:
- return datetime.now()
+ return datetime.datetime.now(utc if settings.USE_TZ else None)
 
 
 # By design, these four functions don't perform any checks on their arguments.