Python django.conf.settings.USE_TZ Examples

def parse_date_input(value):
    """Return datetime based on the user's input.

    @param value: User's input
    @type value: str
    @raise ValueError: If the input is not valid.
    @return: Datetime of the beginning of the user's date.
    """
    try:
        limit = parse_date(value)
    except ValueError:
        limit = None
    if limit is None:
        raise ValueError("'{}' is not a valid date.".format(value))
    limit = datetime(limit.year, limit.month, limit.day)
    if settings.USE_TZ:
        limit = make_aware(limit)
    return limit 

def year_lookup_bounds_for_datetime_field(self, value):
        """
        Return a two-elements list with the lower and upper bound to be used
        with a BETWEEN operator to query a DateTimeField value using a year
        lookup.

        `value` is an int, containing the looked-up year.
        """
        first = datetime.datetime(value, 1, 1)
        second = datetime.datetime(value, 12, 31, 23, 59, 59, 999999)
        if settings.USE_TZ:
            tz = timezone.get_current_timezone()
            first = timezone.make_aware(first, tz)
            second = timezone.make_aware(second, tz)
        first = self.adapt_datetimefield_value(first)
        second = self.adapt_datetimefield_value(second)
        return [first, second] 

def adapt_datetimefield_value(self, value):
        if value is None:
            return None

        # Expression values are adapted by the database.
        if hasattr(value, 'resolve_expression'):
            return value

        # SQLite doesn't support tz-aware datetimes
        if timezone.is_aware(value):
            if settings.USE_TZ:
                value = timezone.make_naive(value, self.connection.timezone)
            else:
                raise ValueError("SQLite backend does not support timezone-aware datetimes when USE_TZ is False.")

        return str(value) 

def timezone(self):
        """
        Time zone for datetimes stored as naive values in the database.

        Return a tzinfo object or None.

        This is only needed when time zone support is enabled and the database
        doesn't support time zones. (When the database supports time zones,
        the adapter handles aware datetimes so Django doesn't need to.)
        """
        if not settings.USE_TZ:
            return None
        elif self.features.supports_timezones:
            return None
        elif self.settings_dict['TIME_ZONE'] is None:
            return timezone.utc
        else:
            return pytz.timezone(self.settings_dict['TIME_ZONE']) 

def adapt_datetime_with_timezone_support(value, conv):
    # Equivalent to DateTimeField.get_db_prep_value. Used only by raw SQL.
    if settings.USE_TZ:
        if timezone.is_naive(value):
            warnings.warn("MySQL received a naive datetime (%s)"
                          " while time zone support is active." % value,
                          RuntimeWarning)
            default_timezone = timezone.get_default_timezone()
            value = timezone.make_aware(value, default_timezone)
        value = value.astimezone(timezone.utc).replace(tzinfo=None)
    return Thing2Literal(value.strftime("%Y-%m-%d %H:%M:%S.%f"), conv)

# MySQLdb-1.2.1 returns TIME columns as timedelta -- they are more like
# timedelta in terms of actual behavior as they are signed and include days --
# and Django expects time, so we still need to override that. We also need to
# add special handling for SafeText and SafeBytes as MySQLdb's type
# checking is too tight to catch those (see Django ticket #6052).
# Finally, MySQLdb always returns naive datetime objects. However, when
# timezone support is active, Django expects timezone-aware datetime objects. 

def datetime_trunc_sql(self, lookup_type, field_name, tzname):
        if settings.USE_TZ:
            field_name = "CONVERT_TZ(%s, 'UTC', %%s)" % field_name
            params = [tzname]
        else:
            params = []
        fields = ['year', 'month', 'day', 'hour', 'minute', 'second']
        format = ('%%Y-', '%%m', '-%%d', ' %%H:', '%%i', ':%%s')  # Use double percents to escape.
        format_def = ('0000-', '01', '-01', ' 00:', '00', ':00')
        try:
            i = fields.index(lookup_type) + 1
        except ValueError:
            sql = field_name
        else:
            format_str = ''.join([f for f in format[:i]] + [f for f in format_def[i:]])
            sql = "CAST(DATE_FORMAT(%s, '%s') AS DATETIME)" % (field_name, format_str)
        return sql, params 

def template_localtime(value, use_tz=None):
    """
    Check if value is a datetime and converts it to local time if necessary.

    If use_tz is provided and is not None, that will force the value to
    be converted (or not), overriding the value of settings.USE_TZ.

    This function is designed for use by the template engine.
    """
    should_convert = (
        isinstance(value, 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)
    )
    return localtime(value) if should_convert else value


# Utilities 

def adapt_datetimefield_value(self, value):
        """
        Transform a datetime value to an object compatible with what is expected
        by the backend driver for datetime columns.

        If naive datetime is passed assumes that is in UTC. Normally Django
        models.DateTimeField makes sure that if USE_TZ is True passed datetime
        is timezone aware.
        """

        if value is None:
            return None

        # Expression values are adapted by the database.
        if hasattr(value, 'resolve_expression'):
            return value

        # cx_Oracle doesn't support tz-aware datetimes
        if timezone.is_aware(value):
            if settings.USE_TZ:
                value = timezone.make_naive(value, self.connection.timezone)
            else:
                raise ValueError("Oracle backend does not support timezone-aware datetimes when USE_TZ is False.")

        return Oracle_datetime.from_datetime(value) 

def from_current_timezone(value):
    """
    When time zone support is enabled, convert naive datetimes
    entered in the current time zone to aware datetimes.
    """
    if settings.USE_TZ and value is not None and timezone.is_naive(value):
        current_timezone = timezone.get_current_timezone()
        try:
            return timezone.make_aware(value, current_timezone)
        except Exception as exc:
            raise ValidationError(
                _('%(datetime)s couldn\'t be interpreted '
                  'in time zone %(current_timezone)s; it '
                  'may be ambiguous or it may not exist.'),
                code='ambiguous_timezone',
                params={'datetime': value, 'current_timezone': current_timezone}
            ) from exc
    return value 

def datetimes(self, field_name, kind, order='ASC', tzinfo=None):
        """
        Returns a list of datetime objects representing all available
        datetimes for the given field_name, scoped to 'kind'.
        """
        assert kind in ("year", "month", "day", "hour", "minute", "second"), \
            "'kind' must be one of 'year', 'month', 'day', 'hour', 'minute' or 'second'."
        assert order in ('ASC', 'DESC'), \
            "'order' must be either 'ASC' or 'DESC'."
        if settings.USE_TZ:
            if tzinfo is None:
                tzinfo = timezone.get_current_timezone()
        else:
            tzinfo = None
        return self.annotate(
            datetimefield=DateTime(field_name, kind, tzinfo),
            plain_field=F(field_name)
        ).values_list(
            'datetimefield', flat=True
        ).distinct().filter(plain_field__isnull=False).order_by(('-' if order == 'DESC' else '') + 'datetimefield') 

def ensure_defaults(self, alias):
        """
        Puts the defaults into the settings dictionary for a given connection
        where no settings is provided.
        """
        try:
            conn = self.databases[alias]
        except KeyError:
            raise ConnectionDoesNotExist("The connection %s doesn't exist" % alias)

        conn.setdefault('ATOMIC_REQUESTS', False)
        conn.setdefault('AUTOCOMMIT', True)
        conn.setdefault('ENGINE', 'django.db.backends.dummy')
        if conn['ENGINE'] == 'django.db.backends.' or not conn['ENGINE']:
            conn['ENGINE'] = 'django.db.backends.dummy'
        conn.setdefault('CONN_MAX_AGE', 0)
        conn.setdefault('OPTIONS', {})
        conn.setdefault('TIME_ZONE', 'UTC' if settings.USE_TZ else settings.TIME_ZONE)
        for setting in ['NAME', 'USER', 'PASSWORD', 'HOST', 'PORT']:
            conn.setdefault(setting, '') 

def get_prep_value(self, value):
        value = super(DateTimeField, self).get_prep_value(value)
        value = self.to_python(value)
        if value is not None and settings.USE_TZ and timezone.is_naive(value):
            # For backwards compatibility, interpret naive datetimes in local
            # time. This won't work during DST change, but we can't do much
            # about it, so we let the exceptions percolate up the call stack.
            try:
                name = '%s.%s' % (self.model.__name__, self.name)
            except AttributeError:
                name = '(unbound)'
            warnings.warn("DateTimeField %s received a naive datetime (%s)"
                          " while time zone support is active." %
                          (name, value),
                          RuntimeWarning)
            default_timezone = timezone.get_default_timezone()
            value = timezone.make_aware(value, default_timezone)
        return value 

def template_localtime(value, use_tz=None):
    """
    Checks if value is a datetime and converts it to local time if necessary.

    If use_tz is provided and is not None, that will force the value to
    be converted (or not), overriding the value of settings.USE_TZ.

    This function is designed for use by the template engine.
    """
    should_convert = (isinstance(value, 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))
    return localtime(value) if should_convert else value


# Utilities 

def from_current_timezone(value):
    """
    When time zone support is enabled, convert naive datetimes
    entered in the current time zone to aware datetimes.
    """
    if settings.USE_TZ and value is not None and timezone.is_naive(value):
        current_timezone = timezone.get_current_timezone()
        try:
            return timezone.make_aware(value, current_timezone)
        except Exception:
            message = _(
                '%(datetime)s couldn\'t be interpreted '
                'in time zone %(current_timezone)s; it '
                'may be ambiguous or it may not exist.'
            )
            params = {'datetime': value, 'current_timezone': current_timezone}
            six.reraise(ValidationError, ValidationError(
                message,
                code='ambiguous_timezone',
                params=params,
            ), sys.exc_info()[2])
    return value 

def _DATETIME_to_python(self, value, dsc=None):
        """Connector/Python always returns naive datetime.datetime

        Connector/Python always returns naive timestamps since MySQL has
        no time zone support. Since Django needs non-naive, we need to add
        the UTC time zone.

        Returns datetime.datetime()
        """
        if not value:
            return None
        dt = MySQLConverter._DATETIME_to_python(self, value)
        if dt is None:
            return None
        if settings.USE_TZ and timezone.is_naive(dt):
            dt = dt.replace(tzinfo=timezone.utc)
        return dt 

def _cull(self, db, cursor, now):
        if self._cull_frequency == 0:
            self.clear()
        else:
            # When USE_TZ is True, 'now' will be an aware datetime in UTC.
            now = now.replace(tzinfo=None)
            table = connections[db].ops.quote_name(self._table)
            cursor.execute("DELETE FROM %s WHERE expires < %%s" % table,
                           [connections[db].ops.value_to_db_datetime(now)])
            cursor.execute("SELECT COUNT(*) FROM %s" % table)
            num = cursor.fetchone()[0]
            if num > self._max_entries:
                cull_num = num // self._cull_frequency
                cursor.execute(
                    connections[db].ops.cache_key_culling_sql() % table,
                    [cull_num])
                cursor.execute("DELETE FROM %s "
                               "WHERE cache_key < %%s" % table,
                               [cursor.fetchone()[0]]) 

def datetime_extract_sql(self, lookup_type, field_name, tzname):
        # Django 1.6
        if settings.USE_TZ:
            field_name = "CONVERT_TZ({0}, 'UTC', %s)".format(field_name)
            params = [tzname]
        else:
            params = []

        # http://dev.mysql.com/doc/mysql/en/date-and-time-functions.html
        if lookup_type == 'week_day':
            # DAYOFWEEK() returns an integer, 1-7, Sunday=1.
            # Note: WEEKDAY() returns 0-6, Monday=0.
            sql = "DAYOFWEEK({0})".format(field_name)
        else:
            sql = "EXTRACT({0} FROM {1})".format(lookup_type.upper(),
                                                 field_name)
        return sql, params 

def datetime_trunc_sql(self, lookup_type, field_name, tzname):
        # Django 1.6
        if settings.USE_TZ:
            field_name = "CONVERT_TZ({0}, 'UTC', %s)".format(field_name)
            params = [tzname]
        else:
            params = []
        fields = ['year', 'month', 'day', 'hour', 'minute', 'second']
        format_ = ('%Y-', '%m', '-%d', ' %H:', '%i', ':%S')
        format_def = ('0000-', '01', '-01', ' 00:', '00', ':00')
        try:
            i = fields.index(lookup_type) + 1
        except ValueError:
            sql = field_name
        else:
            format_str = ''.join([f for f in format_[:i]] +
                                 [f for f in format_def[i:]])
            sql = "CAST(DATE_FORMAT({0}, '{1}') AS DATETIME)".format(
                field_name, format_str)
        return sql, params 

def __init__(self, environment):
        super(DjangoL10n, self).__init__(environment)
        finalize = []
        if settings.USE_TZ:
            finalize.append(template_localtime)
        if settings.USE_L10N:
            finalize.append(localize)

        if finalize:
            fns = iter(finalize)
            if environment.finalize is None:
                new_finalize = next(fns)
            else:
                new_finalize = environment.finalize
            for f in fns:
                new_finalize = self._compose(f, new_finalize)

            environment.finalize = new_finalize 

def get_prep_value(self, value):
        value = super().get_prep_value(value)
        value = self.to_python(value)
        if value is not None and settings.USE_TZ and timezone.is_naive(value):
            # For backwards compatibility, interpret naive datetimes in local
            # time. This won't work during DST change, but we can't do much
            # about it, so we let the exceptions percolate up the call stack.
            try:
                name = '%s.%s' % (self.model.__name__, self.name)
            except AttributeError:
                name = '(unbound)'
            warnings.warn("DateTimeField %s received a naive datetime (%s)"
                          " while time zone support is active." %
                          (name, value),
                          RuntimeWarning)
            default_timezone = timezone.get_default_timezone()
            value = timezone.make_aware(value, default_timezone)
        return value 

def datetime(self, field=None, val=None):
        """
        Returns a random datetime. If 'val' is passed, a datetime within two
        years of that date will be returned.
        """
        if val is None:
            def source():
                tzinfo = get_default_timezone() if settings.USE_TZ else None
                return datetime.fromtimestamp(randrange(1, 2100000000),
                                              tzinfo)
        else:
            def source():
                tzinfo = get_default_timezone() if settings.USE_TZ else None
                return datetime.fromtimestamp(int(val.strftime("%s")) +
                                              randrange(-365*24*3600*2, 365*24*3600*2),
                                              tzinfo)
        return self.get_allowed_value(source, field) 

def convert_value(self, value, expression, connection):
        if isinstance(self.output_field, DateTimeField):
            if settings.USE_TZ:
                if value is None:
                    raise ValueError(
                        "Database returned an invalid datetime value. "
                        "Are time zone definitions for your database installed?"
                    )
                value = value.replace(tzinfo=None)
                value = timezone.make_aware(value, self.tzinfo)
        elif isinstance(value, datetime):
            if isinstance(self.output_field, DateField):
                value = value.date()
            elif isinstance(self.output_field, TimeField):
                value = value.time()
        return value 

def to_current_timezone(value):
    """
    When time zone support is enabled, convert aware datetimes
    to naive datetimes in the current time zone for display.
    """
    if settings.USE_TZ and value is not None and timezone.is_aware(value):
        current_timezone = timezone.get_current_timezone()
        return timezone.make_naive(value, current_timezone)
    return value 

def _now(self, format_string):
        tzinfo = get_current_timezone() if settings.USE_TZ else None
        cur_datetime = datetime.now(tz=tzinfo)
        return date_format(cur_datetime, format_string) 

def _make_date_lookup_arg(self, value):
        """
        Convert a date into a datetime when the date field is a DateTimeField.

        When time zone support is enabled, `date` is assumed to be in the
        current time zone, so that displayed items are consistent with the URL.
        """
        if self.uses_datetime_field:
            value = datetime.datetime.combine(value, datetime.time.min)
            if settings.USE_TZ:
                value = timezone.make_aware(value, timezone.get_current_timezone())
        return value 

def _i18n_cache_key_suffix(request, cache_key):
    """If necessary, add the current locale or time zone to the cache key."""
    if settings.USE_I18N or settings.USE_L10N:
        # first check if LocaleMiddleware or another middleware added
        # LANGUAGE_CODE to request, then fall back to the active language
        # which in turn can also fall back to settings.LANGUAGE_CODE
        cache_key += '.%s' % getattr(request, 'LANGUAGE_CODE', get_language())
    if settings.USE_TZ:
        # The datetime module doesn't restrict the output of tzname().
        # Windows is known to use non-standard, locale-dependent names.
        # User-defined tzinfo classes may return absolutely anything.
        # Hence this paranoid conversion to create a valid cache key.
        tz_name = force_text(get_current_timezone_name(), errors='ignore')
        cache_key += '.%s' % tz_name.encode('ascii', 'ignore').decode('ascii').replace(' ', '_')
    return cache_key 

def timezone_today():
    """Return the current date in the current time zone."""
    if settings.USE_TZ:
        return timezone.localdate()
    else:
        return datetime.date.today() 

def init_connection_state(self):
        cursor = self.create_cursor()
        # Set the territory first. The territory overrides NLS_DATE_FORMAT
        # and NLS_TIMESTAMP_FORMAT to the territory default. When all of
        # these are set in single statement it isn't clear what is supposed
        # to happen.
        cursor.execute("ALTER SESSION SET NLS_TERRITORY = 'AMERICA'")
        # Set Oracle date to ANSI date format.  This only needs to execute
        # once when we create a new connection. We also set the Territory
        # to 'AMERICA' which forces Sunday to evaluate to a '1' in
        # TO_CHAR().
        cursor.execute(
            "ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD HH24:MI:SS'"
            " NLS_TIMESTAMP_FORMAT = 'YYYY-MM-DD HH24:MI:SS.FF'" +
            (" TIME_ZONE = 'UTC'" if settings.USE_TZ else '')
        )
        cursor.close()
        if 'operators' not in self.__dict__:
            # Ticket #14149: Check whether our LIKE implementation will
            # work for this connection or we need to fall back on LIKEC.
            # This check is performed only once per DatabaseWrapper
            # instance per thread, since subsequent connections will use
            # the same settings.
            cursor = self.create_cursor()
            try:
                cursor.execute("SELECT 1 FROM DUAL WHERE DUMMY %s"
                               % self._standard_operators['contains'],
                               ['X'])
            except Database.DatabaseError:
                self.operators = self._likec_operators
                self.pattern_ops = self._likec_pattern_ops
            else:
                self.operators = self._standard_operators
                self.pattern_ops = self._standard_pattern_ops
            cursor.close()
        self.connection.stmtcachesize = 20
        # Ensure all changes are preserved even when AUTOCOMMIT is False.
        if not self.get_autocommit():
            self.commit() 

def timezone_name(self):
        """
        Name of the time zone of the database connection.
        """
        if not settings.USE_TZ:
            return settings.TIME_ZONE
        elif self.settings_dict['TIME_ZONE'] is None:
            return 'UTC'
        else:
            return self.settings_dict['TIME_ZONE'] 

def get_tzname(self):
        # Timezone conversions must happen to the input datetime *before*
        # applying a function. 2015-12-31 23:00:00 -02:00 is stored in the
        # database as 2016-01-01 01:00:00 +00:00. Any results should be
        # based on the input datetime not the stored datetime.
        tzname = None
        if settings.USE_TZ:
            if self.tzinfo is None:
                tzname = timezone.get_current_timezone_name()
            else:
                tzname = timezone._get_timezone_name(self.tzinfo)
        return tzname