Class RRuleLocator

lib/matplotlib/dates.py:1140–1213

class RRuleLocator(DateLocator):
    # use the dateutil rrule instance

    def __init__(self, o, tz=None):
        super().__init__(tz)
        self.rule = o

    def __call__(self):
        # if no data have been set, this will tank with a ValueError
        try:
            dmin, dmax = self.viewlim_to_dt()
        except ValueError:
            return []

        return self.tick_values(dmin, dmax)

    def tick_values(self, vmin, vmax):
        start, stop = self._create_rrule(vmin, vmax)
        dates = self.rule.between(start, stop, True)
        if len(dates) == 0:
            return date2num([vmin, vmax])
        return self.raise_if_exceeds(date2num(dates))

    def _create_rrule(self, vmin, vmax):
        # set appropriate rrule dtstart and until and return
        # start and end
        delta = relativedelta(vmax, vmin)

        # We need to cap at the endpoints of valid datetime
        try:
            start = vmin - delta
        except (ValueError, OverflowError):
            # cap
            start = datetime.datetime(1, 1, 1, 0, 0, 0,
                                      tzinfo=datetime.timezone.utc)

        try:
            stop = vmax + delta
        except (ValueError, OverflowError):
            # cap
            stop = datetime.datetime(9999, 12, 31, 23, 59, 59,
                                     tzinfo=datetime.timezone.utc)

        self.rule.set(dtstart=start, until=stop)

        return vmin, vmax

    def _get_unit(self):
        # docstring inherited
        freq = self.rule._rrule._freq
        return self.get_unit_generic(freq)

    @staticmethod
    def get_unit_generic(freq):
        if freq == YEARLY:
            return DAYS_PER_YEAR
        elif freq == MONTHLY:
            return DAYS_PER_MONTH