Пример #1
0
    def test_make_naive(self):
        self.assertEqual(
            timezone.make_naive(datetime.datetime(2011, 9, 1, 13, 20, 30, tzinfo=EAT), EAT),
            datetime.datetime(2011, 9, 1, 13, 20, 30))
        self.assertEqual(
            timezone.make_naive(datetime.datetime(2011, 9, 1, 17, 20, 30, tzinfo=ICT), EAT),
            datetime.datetime(2011, 9, 1, 13, 20, 30))

        with self.assertRaises(ValueError):
            timezone.make_naive(datetime.datetime(2011, 9, 1, 13, 20, 30), EAT)
Пример #2
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    def test_make_naive(self):
        assert timezone.make_naive(
            datetime.datetime(2011, 9, 1, 13, 20, 30, tzinfo=EAT), EAT
        ) == datetime.datetime(2011, 9, 1, 13, 20, 30)
        assert timezone.make_naive(
            datetime.datetime(2011, 9, 1, 17, 20, 30, tzinfo=ICT), EAT
        ) == datetime.datetime(2011, 9, 1, 13, 20, 30)

        with pytest.raises(ValueError):
            timezone.make_naive(datetime.datetime(2011, 9, 1, 13, 20, 30), EAT)
Пример #3
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    def test_make_naive(self):
        self.assertEqual(
            timezone.make_naive(
                datetime.datetime(2011, 9, 1, 13, 20, 30, tzinfo=EAT), EAT),
            datetime.datetime(2011, 9, 1, 13, 20, 30))
        self.assertEqual(
            timezone.make_naive(
                datetime.datetime(2011, 9, 1, 17, 20, 30, tzinfo=ICT), EAT),
            datetime.datetime(2011, 9, 1, 13, 20, 30))

        with self.assertRaises(ValueError):
            timezone.make_naive(datetime.datetime(2011, 9, 1, 13, 20, 30), EAT)
Пример #4
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    def choose_branch(self, context: Context) -> Union[str, Iterable[str]]:
        if self.use_task_execution_date is True:
            now = timezone.make_naive(context["logical_date"], self.dag.timezone)
        else:
            now = timezone.make_naive(timezone.utcnow(), self.dag.timezone)

        lower, upper = target_times_as_dates(now, self.target_lower, self.target_upper)
        if upper is not None and upper < now:
            return self.follow_task_ids_if_false

        if lower is not None and lower > now:
            return self.follow_task_ids_if_false

        return self.follow_task_ids_if_true
Пример #5
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    def test_set_dag_run_state_edge_cases(self):
        # Dag does not exist
        altered = set_dag_run_state_to_success(None, self.execution_dates[0])
        assert len(altered) == 0
        altered = set_dag_run_state_to_failed(None, self.execution_dates[0])
        assert len(altered) == 0
        altered = set_dag_run_state_to_running(None, self.execution_dates[0])
        assert len(altered) == 0

        # Invalid execution date
        altered = set_dag_run_state_to_success(self.dag1, None)
        assert len(altered) == 0
        altered = set_dag_run_state_to_failed(self.dag1, None)
        assert len(altered) == 0
        altered = set_dag_run_state_to_running(self.dag1, None)
        assert len(altered) == 0

        # This will throw ValueError since dag.latest_execution_date
        # need to be 0 does not exist.
        with pytest.raises(ValueError):
            set_dag_run_state_to_success(
                self.dag2, timezone.make_naive(self.execution_dates[0]))
        # altered = set_dag_run_state_to_success(self.dag1, self.execution_dates[0])
        # DagRun does not exist
        # This will throw ValueError since dag.latest_execution_date does not exist
        with pytest.raises(ValueError):
            set_dag_run_state_to_success(self.dag2, self.execution_dates[0])
    def test_set_dag_run_state_edge_cases(self):
        # Dag does not exist
        altered = set_dag_run_state_to_success(None, self.execution_dates[0])
        self.assertEqual(len(altered), 0)
        altered = set_dag_run_state_to_failed(None, self.execution_dates[0])
        self.assertEqual(len(altered), 0)
        altered = set_dag_run_state_to_running(None, self.execution_dates[0])
        self.assertEqual(len(altered), 0)

        # Invalid execution date
        altered = set_dag_run_state_to_success(self.dag1, None)
        self.assertEqual(len(altered), 0)
        altered = set_dag_run_state_to_failed(self.dag1, None)
        self.assertEqual(len(altered), 0)
        altered = set_dag_run_state_to_running(self.dag1, None)
        self.assertEqual(len(altered), 0)

        # This will throw ValueError since dag.latest_execution_date
        # need to be 0 does not exist.
        self.assertRaises(ValueError, set_dag_run_state_to_success, self.dag2,
                          timezone.make_naive(self.execution_dates[0]))
        # altered = set_dag_run_state_to_success(self.dag1, self.execution_dates[0])
        # DagRun does not exist
        # This will throw ValueError since dag.latest_execution_date does not exist
        self.assertRaises(ValueError, set_dag_run_state_to_success, self.dag2,
                          self.execution_dates[0])
Пример #7
0
    def test_set_dag_run_state_edge_cases(self):
        # Dag does not exist
        altered = set_dag_run_state_to_success(None, self.execution_dates[0])
        self.assertEqual(len(altered), 0)
        altered = set_dag_run_state_to_failed(None, self.execution_dates[0])
        self.assertEqual(len(altered), 0)
        altered = set_dag_run_state_to_running(None, self.execution_dates[0])
        self.assertEqual(len(altered), 0)

        # Invalid execution date
        altered = set_dag_run_state_to_success(self.dag1, None)
        self.assertEqual(len(altered), 0)
        altered = set_dag_run_state_to_failed(self.dag1, None)
        self.assertEqual(len(altered), 0)
        altered = set_dag_run_state_to_running(self.dag1, None)
        self.assertEqual(len(altered), 0)

        # This will throw AssertionError since dag.latest_execution_date
        # need to be 0 does not exist.
        self.assertRaises(AssertionError, set_dag_run_state_to_success, self.dag1,
                          timezone.make_naive(self.execution_dates[0]))

        # altered = set_dag_run_state_to_success(self.dag1, self.execution_dates[0])
        # DagRun does not exist
        # This will throw AssertionError since dag.latest_execution_date does not exist
        self.assertRaises(AssertionError, set_dag_run_state_to_success,
                          self.dag1, self.execution_dates[0])
Пример #8
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 def __init__(self, *, target_time, **kwargs):
     super().__init__(**kwargs)
     self.target_time = target_time
     current_time = timezone.make_naive(timezone.utcnow(),
                                        self.dag.timezone)
     todays_date = current_time.date()
     self.target_datetime = datetime.datetime.combine(
         todays_date, self.target_time, current_time.tzinfo)
Пример #9
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    def choose_branch(self, context: Context) -> Union[str, Iterable[str]]:
        if self.use_task_execution_day:
            now = context["logical_date"]
        else:
            now = timezone.make_naive(timezone.utcnow(), self.dag.timezone)

        if now.isoweekday() in self._week_day_num:
            return self.follow_task_ids_if_true
        return self.follow_task_ids_if_false
Пример #10
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 def _get_prev(self, current: DateTime) -> DateTime:
     """Get the first schedule before specified time, with DST fixed."""
     naive = make_naive(current, self._timezone)
     cron = croniter(self._expression, start_time=naive)
     scheduled = cron.get_prev(datetime.datetime)
     if not self._should_fix_dst:
         return convert_to_utc(make_aware(scheduled, self._timezone))
     delta = naive - scheduled
     return convert_to_utc(current.in_timezone(self._timezone) - delta)
Пример #11
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 def process_bind_param(self, value, dialect):
     if value is not None:
         if not isinstance(value, datetime.datetime):
             raise TypeError('expected datetime.datetime, not ' +
                             repr(value))
         elif value.tzinfo is None:
             raise ValueError('naive datetime is disallowed')
         # For mysql we should store timestamps as naive values
         # Timestamp in MYSQL is not timezone aware. In MySQL 5.6
         # timezone added at the end is ignored but in MySQL 5.7
         # inserting timezone value fails with 'invalid-date'
         # See https://issues.apache.org/jira/browse/AIRFLOW-7001
         if using_mysql:
             from airflow.utils.timezone import make_naive
             return make_naive(value, timezone=utc)
         return value.astimezone(utc)
Пример #12
0
def date_range(start_date, end_date=None, num=None, delta=None):
    """
    Get a set of dates as a list based on a start, end and delta, delta
    can be something that can be added to ``datetime.datetime``
    or a cron expression as a ``str``

    :param start_date: anchor date to start the series from
    :type start_date: datetime.datetime
    :param end_date: right boundary for the date range
    :type end_date: datetime.datetime
    :param num: alternatively to end_date, you can specify the number of
        number of entries you want in the range. This number can be negative,
        output will always be sorted regardless
    :type num: int

    >>> date_range(datetime(2016, 1, 1), datetime(2016, 1, 3), delta=timedelta(1))
    [datetime.datetime(2016, 1, 1, 0, 0), datetime.datetime(2016, 1, 2, 0, 0), datetime.datetime(2016, 1, 3, 0, 0)]
    >>> date_range(datetime(2016, 1, 1), datetime(2016, 1, 3), delta='0 0 * * *')
    [datetime.datetime(2016, 1, 1, 0, 0), datetime.datetime(2016, 1, 2, 0, 0), datetime.datetime(2016, 1, 3, 0, 0)]
    >>> date_range(datetime(2016, 1, 1), datetime(2016, 3, 3), delta="0 0 0 * *")
    [datetime.datetime(2016, 1, 1, 0, 0), datetime.datetime(2016, 2, 1, 0, 0), datetime.datetime(2016, 3, 1, 0, 0)]
    """
    if not delta:
        return []
    if end_date and start_date > end_date:
        raise Exception("Wait. start_date needs to be before end_date")
    if end_date and num:
        raise Exception("Wait. Either specify end_date OR num")
    if not end_date and not num:
        end_date = timezone.utcnow()

    delta_iscron = False
    if isinstance(delta, six.string_types):
        delta_iscron = True
        tz = start_date.tzinfo
        start_date = timezone.make_naive(start_date, tz)
        cron = croniter(delta, start_date)
    elif isinstance(delta, timedelta):
        delta = abs(delta)
    l = []
    if end_date:
        while start_date <= end_date:
            if timezone.is_naive(start_date):
                l.append(timezone.make_aware(start_date, tz))
            else:
                l.append(start_date)

            if delta_iscron:
                start_date = cron.get_next(datetime)
            else:
                start_date += delta
    else:
        for _ in range(abs(num)):
            if timezone.is_naive(start_date):
                l.append(timezone.make_aware(start_date, tz))
            else:
                l.append(start_date)

            if delta_iscron:
                if num > 0:
                    start_date = cron.get_next(datetime)
                else:
                    start_date = cron.get_prev(datetime)
            else:
                if num > 0:
                    start_date += delta
                else:
                    start_date -= delta
    return sorted(l)
Пример #13
0
def round_time(dt, delta, start_date=timezone.make_aware(datetime.min)):
    """
    Returns the datetime of the form start_date + i * delta
    which is closest to dt for any non-negative integer i.

    Note that delta may be a datetime.timedelta or a dateutil.relativedelta

    >>> round_time(datetime(2015, 1, 1, 6), timedelta(days=1))
    datetime.datetime(2015, 1, 1, 0, 0)
    >>> round_time(datetime(2015, 1, 2), relativedelta(months=1))
    datetime.datetime(2015, 1, 1, 0, 0)
    >>> round_time(datetime(2015, 9, 16, 0, 0), timedelta(1), datetime(2015, 9, 14, 0, 0))
    datetime.datetime(2015, 9, 16, 0, 0)
    >>> round_time(datetime(2015, 9, 15, 0, 0), timedelta(1), datetime(2015, 9, 14, 0, 0))
    datetime.datetime(2015, 9, 15, 0, 0)
    >>> round_time(datetime(2015, 9, 14, 0, 0), timedelta(1), datetime(2015, 9, 14, 0, 0))
    datetime.datetime(2015, 9, 14, 0, 0)
    >>> round_time(datetime(2015, 9, 13, 0, 0), timedelta(1), datetime(2015, 9, 14, 0, 0))
    datetime.datetime(2015, 9, 14, 0, 0)
    """

    if isinstance(delta, six.string_types):
        # It's cron based, so it's easy
        tz = start_date.tzinfo
        start_date = timezone.make_naive(start_date, tz)
        cron = croniter(delta, start_date)
        prev = cron.get_prev(datetime)
        if prev == start_date:
            return timezone.make_aware(start_date, tz)
        else:
            return timezone.make_aware(prev, tz)

    # Ignore the microseconds of dt
    dt -= timedelta(microseconds=dt.microsecond)

    # We are looking for a datetime in the form start_date + i * delta
    # which is as close as possible to dt. Since delta could be a relative
    # delta we don't know it's exact length in seconds so we cannot rely on
    # division to find i. Instead we employ a binary search algorithm, first
    # finding an upper and lower limit and then disecting the interval until
    # we have found the closest match.

    # We first search an upper limit for i for which start_date + upper * delta
    # exceeds dt.
    upper = 1
    while start_date + upper * delta < dt:
        # To speed up finding an upper limit we grow this exponentially by a
        # factor of 2
        upper *= 2

    # Since upper is the first value for which start_date + upper * delta
    # exceeds dt, upper // 2 is below dt and therefore forms a lower limited
    # for the i we are looking for
    lower = upper // 2

    # We now continue to intersect the interval between
    # start_date + lower * delta and start_date + upper * delta
    # until we find the closest value
    while True:
        # Invariant: start + lower * delta < dt <= start + upper * delta
        # If start_date + (lower + 1)*delta exceeds dt, then either lower or
        # lower+1 has to be the solution we are searching for
        if start_date + (lower + 1) * delta >= dt:
            # Check if start_date + (lower + 1)*delta or
            # start_date + lower*delta is closer to dt and return the solution
            if ((start_date + (lower + 1) * delta) - dt <= dt -
                (start_date + lower * delta)):
                return start_date + (lower + 1) * delta
            else:
                return start_date + lower * delta

        # We intersect the interval and either replace the lower or upper
        # limit with the candidate
        candidate = lower + (upper - lower) // 2
        if start_date + candidate * delta >= dt:
            upper = candidate
        else:
            lower = candidate
Пример #14
0
def round_time(dt, delta, start_date=timezone.make_aware(datetime.min)):
    """
    Returns the datetime of the form start_date + i * delta
    which is closest to dt for any non-negative integer i.
    Note that delta may be a datetime.timedelta or a dateutil.relativedelta
    >>> round_time(datetime(2015, 1, 1, 6), timedelta(days=1))
    datetime.datetime(2015, 1, 1, 0, 0)
    >>> round_time(datetime(2015, 1, 2), relativedelta(months=1))
    datetime.datetime(2015, 1, 1, 0, 0)
    >>> round_time(datetime(2015, 9, 16, 0, 0), timedelta(1), datetime(2015, 9, 14, 0, 0))
    datetime.datetime(2015, 9, 16, 0, 0)
    >>> round_time(datetime(2015, 9, 15, 0, 0), timedelta(1), datetime(2015, 9, 14, 0, 0))
    datetime.datetime(2015, 9, 15, 0, 0)
    >>> round_time(datetime(2015, 9, 14, 0, 0), timedelta(1), datetime(2015, 9, 14, 0, 0))
    datetime.datetime(2015, 9, 14, 0, 0)
    >>> round_time(datetime(2015, 9, 13, 0, 0), timedelta(1), datetime(2015, 9, 14, 0, 0))
    datetime.datetime(2015, 9, 14, 0, 0)
    """

    if isinstance(delta, six.string_types):
        # It's cron based, so it's easy
        tz = start_date.tzinfo
        start_date = timezone.make_naive(start_date, tz)
        cron = croniter(delta, start_date)
        prev = cron.get_prev(datetime)
        if prev == start_date:
            return timezone.make_aware(start_date, tz)
        else:
            return timezone.make_aware(prev, tz)

    # Ignore the microseconds of dt
    dt -= timedelta(microseconds=dt.microsecond)

    # We are looking for a datetime in the form start_date + i * delta
    # which is as close as possible to dt. Since delta could be a relative
    # delta we don't know its exact length in seconds so we cannot rely on
    # division to find i. Instead we employ a binary search algorithm, first
    # finding an upper and lower limit and then disecting the interval until
    # we have found the closest match.

    # We first search an upper limit for i for which start_date + upper * delta
    # exceeds dt.
    upper = 1
    while start_date + upper * delta < dt:
        # To speed up finding an upper limit we grow this exponentially by a
        # factor of 2
        upper *= 2

    # Since upper is the first value for which start_date + upper * delta
    # exceeds dt, upper // 2 is below dt and therefore forms a lower limited
    # for the i we are looking for
    lower = upper // 2

    # We now continue to intersect the interval between
    # start_date + lower * delta and start_date + upper * delta
    # until we find the closest value
    while True:
        # Invariant: start + lower * delta < dt <= start + upper * delta
        # If start_date + (lower + 1)*delta exceeds dt, then either lower or
        # lower+1 has to be the solution we are searching for
        if start_date + (lower + 1) * delta >= dt:
            # Check if start_date + (lower + 1)*delta or
            # start_date + lower*delta is closer to dt and return the solution
            if (
                    (start_date + (lower + 1) * delta) - dt <=
                    dt - (start_date + lower * delta)):
                return start_date + (lower + 1) * delta
            else:
                return start_date + lower * delta

        # We intersect the interval and either replace the lower or upper
        # limit with the candidate
        candidate = lower + (upper - lower) // 2
        if start_date + candidate * delta >= dt:
            upper = candidate
        else:
            lower = candidate
Пример #15
0
def date_range(
    start_date: datetime,
    end_date: Optional[datetime] = None,
    num: Optional[int] = None,
    delta: Optional[Union[str, timedelta, relativedelta]] = None,
) -> List[datetime]:
    """
    Get a set of dates as a list based on a start, end and delta, delta
    can be something that can be added to `datetime.datetime`
    or a cron expression as a `str`

    .. code-block:: pycon
        >>> from airflow.utils.dates import datterange
        >>> from datetime import datetime, timedelta
        >>> date_range(datetime(2016, 1, 1), datetime(2016, 1, 3), delta=timedelta(1))
        [datetime.datetime(2016, 1, 1, 0, 0, tzinfo=Timezone('UTC')),
        datetime.datetime(2016, 1, 2, 0, 0, tzinfo=Timezone('UTC')),
        datetime.datetime(2016, 1, 3, 0, 0, tzinfo=Timezone('UTC'))]
        >>> date_range(datetime(2016, 1, 1), datetime(2016, 1, 3), delta="0 0 * * *")
        [datetime.datetime(2016, 1, 1, 0, 0, tzinfo=Timezone('UTC')),
        datetime.datetime(2016, 1, 2, 0, 0, tzinfo=Timezone('UTC')),
        datetime.datetime(2016, 1, 3, 0, 0, tzinfo=Timezone('UTC'))]
        >>> date_range(datetime(2016, 1, 1), datetime(2016, 3, 3), delta="0 0 0 * *")
        [datetime.datetime(2016, 1, 1, 0, 0, tzinfo=Timezone('UTC')),
        datetime.datetime(2016, 2, 1, 0, 0, tzinfo=Timezone('UTC')),
        datetime.datetime(2016, 3, 1, 0, 0, tzinfo=Timezone('UTC'))]

    :param start_date: anchor date to start the series from
    :param end_date: right boundary for the date range
    :param num: alternatively to end_date, you can specify the number of
        number of entries you want in the range. This number can be negative,
        output will always be sorted regardless
    :param delta: step length. It can be datetime.timedelta or cron expression as string
    """
    warnings.warn(
        "`airflow.utils.dates.date_range()` is deprecated. Please use `airflow.timetables`.",
        category=DeprecationWarning,
        stacklevel=2,
    )

    if not delta:
        return []
    if end_date:
        if start_date > end_date:
            raise Exception("Wait. start_date needs to be before end_date")
        if num:
            raise Exception("Wait. Either specify end_date OR num")
    if not end_date and not num:
        end_date = timezone.utcnow()

    delta_iscron = False
    time_zone = start_date.tzinfo

    abs_delta: Union[timedelta, relativedelta]
    if isinstance(delta, str):
        delta_iscron = True
        if timezone.is_localized(start_date):
            start_date = timezone.make_naive(start_date, time_zone)
        cron = croniter(cron_presets.get(delta, delta), start_date)
    elif isinstance(delta, timedelta):
        abs_delta = abs(delta)
    elif isinstance(delta, relativedelta):
        abs_delta = abs(delta)
    else:
        raise Exception(
            "Wait. delta must be either datetime.timedelta or cron expression as str"
        )

    dates = []
    if end_date:
        if timezone.is_naive(start_date) and not timezone.is_naive(end_date):
            end_date = timezone.make_naive(end_date, time_zone)
        while start_date <= end_date:  # type: ignore
            if timezone.is_naive(start_date):
                dates.append(timezone.make_aware(start_date, time_zone))
            else:
                dates.append(start_date)

            if delta_iscron:
                start_date = cron.get_next(datetime)
            else:
                start_date += abs_delta
    else:
        num_entries: int = num  # type: ignore
        for _ in range(abs(num_entries)):
            if timezone.is_naive(start_date):
                dates.append(timezone.make_aware(start_date, time_zone))
            else:
                dates.append(start_date)

            if delta_iscron and num_entries > 0:
                start_date = cron.get_next(datetime)
            elif delta_iscron:
                start_date = cron.get_prev(datetime)
            elif num_entries > 0:
                start_date += abs_delta
            else:
                start_date -= abs_delta

    return sorted(dates)
Пример #16
0
def date_range(
        start_date,
        end_date=None,
        num=None,
        delta=None):
    """
    Get a set of dates as a list based on a start, end and delta, delta
    can be something that can be added to ``datetime.datetime``
    or a cron expression as a ``str``
    :param start_date: anchor date to start the series from
    :type start_date: datetime.datetime
    :param end_date: right boundary for the date range
    :type end_date: datetime.datetime
    :param num: alternatively to end_date, you can specify the number of
        number of entries you want in the range. This number can be negative,
        output will always be sorted regardless
    :type num: int
    >>> date_range(datetime(2016, 1, 1), datetime(2016, 1, 3), delta=timedelta(1))
    [datetime.datetime(2016, 1, 1, 0, 0), datetime.datetime(2016, 1, 2, 0, 0),
     datetime.datetime(2016, 1, 3, 0, 0)]
    >>> date_range(datetime(2016, 1, 1), datetime(2016, 1, 3), delta='0 0 * * *')
    [datetime.datetime(2016, 1, 1, 0, 0), datetime.datetime(2016, 1, 2, 0, 0),
     datetime.datetime(2016, 1, 3, 0, 0)]
    >>> date_range(datetime(2016, 1, 1), datetime(2016, 3, 3), delta="0 0 0 * *")
    [datetime.datetime(2016, 1, 1, 0, 0), datetime.datetime(2016, 2, 1, 0, 0),
     datetime.datetime(2016, 3, 1, 0, 0)]
    """
    if not delta:
        return []
    if end_date and start_date > end_date:
        raise Exception("Wait. start_date needs to be before end_date")
    if end_date and num:
        raise Exception("Wait. Either specify end_date OR num")
    if not end_date and not num:
        end_date = timezone.utcnow()

    delta_iscron = False
    tz = start_date.tzinfo
    if isinstance(delta, six.string_types):
        delta_iscron = True
        start_date = timezone.make_naive(start_date, tz)
        cron = croniter(delta, start_date)
    elif isinstance(delta, timedelta):
        delta = abs(delta)
    dates = []
    if end_date:
        if timezone.is_naive(start_date):
            end_date = timezone.make_naive(end_date, tz)
        while start_date <= end_date:
            if timezone.is_naive(start_date):
                dates.append(timezone.make_aware(start_date, tz))
            else:
                dates.append(start_date)

            if delta_iscron:
                start_date = cron.get_next(datetime)
            else:
                start_date += delta
    else:
        for _ in range(abs(num)):
            if timezone.is_naive(start_date):
                dates.append(timezone.make_aware(start_date, tz))
            else:
                dates.append(start_date)

            if delta_iscron:
                if num > 0:
                    start_date = cron.get_next(datetime)
                else:
                    start_date = cron.get_prev(datetime)
            else:
                if num > 0:
                    start_date += delta
                else:
                    start_date -= delta
    return sorted(dates)
Пример #17
0
 def poke(self, context: Context):
     self.log.info('Checking if the time (%s) has come', self.target_time)
     return timezone.make_naive(timezone.utcnow(),
                                self.dag.timezone).time() > self.target_time
Пример #18
0
def date_range(start_date, end_date=None, num=None, delta=None):  # pylint: disable=too-many-branches
    """
    Get a set of dates as a list based on a start, end and delta, delta
    can be something that can be added to `datetime.datetime`
    or a cron expression as a `str`

    .. code-block:: python

        date_range(datetime(2016, 1, 1), datetime(2016, 1, 3), delta=timedelta(1))
            [datetime.datetime(2016, 1, 1, 0, 0), datetime.datetime(2016, 1, 2, 0, 0),
            datetime.datetime(2016, 1, 3, 0, 0)]
        date_range(datetime(2016, 1, 1), datetime(2016, 1, 3), delta='0 0 * * *')
            [datetime.datetime(2016, 1, 1, 0, 0), datetime.datetime(2016, 1, 2, 0, 0),
            datetime.datetime(2016, 1, 3, 0, 0)]
        date_range(datetime(2016, 1, 1), datetime(2016, 3, 3), delta="0 0 0 * *")
            [datetime.datetime(2016, 1, 1, 0, 0), datetime.datetime(2016, 2, 1, 0, 0),
            datetime.datetime(2016, 3, 1, 0, 0)]

    :param start_date: anchor date to start the series from
    :type start_date: datetime.datetime
    :param end_date: right boundary for the date range
    :type end_date: datetime.datetime
    :param num: alternatively to end_date, you can specify the number of
        number of entries you want in the range. This number can be negative,
        output will always be sorted regardless
    :type num: int
    :param delta: step length. It can be datetime.timedelta or cron expression as string
    :type delta: datetime.timedelta or str
    """
    if not delta:
        return []
    if end_date and start_date > end_date:
        raise Exception("Wait. start_date needs to be before end_date")
    if end_date and num:
        raise Exception("Wait. Either specify end_date OR num")
    if not end_date and not num:
        end_date = timezone.utcnow()
    if delta in cron_presets:
        delta = cron_presets.get(delta)

    delta_iscron = False
    time_zone = start_date.tzinfo

    if isinstance(delta, str):
        delta_iscron = True
        if timezone.is_localized(start_date):
            start_date = timezone.make_naive(start_date, time_zone)
        cron = croniter(delta, start_date)
    elif isinstance(delta, timedelta):
        delta = abs(delta)
    else:
        raise Exception(
            "Wait. delta must be either datetime.timedelta or cron expression as str"
        )

    dates = []
    if end_date:
        if timezone.is_naive(start_date) and not timezone.is_naive(end_date):
            end_date = timezone.make_naive(end_date, time_zone)
        while start_date <= end_date:
            if timezone.is_naive(start_date):
                dates.append(timezone.make_aware(start_date, time_zone))
            else:
                dates.append(start_date)

            if delta_iscron:
                start_date = cron.get_next(datetime)
            else:
                start_date += delta
    else:
        for _ in range(abs(num)):
            if timezone.is_naive(start_date):
                dates.append(timezone.make_aware(start_date, time_zone))
            else:
                dates.append(start_date)

            if delta_iscron and num > 0:
                start_date = cron.get_next(datetime)
            elif delta_iscron:
                start_date = cron.get_prev(datetime)
            elif num > 0:
                start_date += delta
            else:
                start_date -= delta

    return sorted(dates)