relativedelta.py 文件源码

def __radd__(self, other):
        if not isinstance(other, datetime.date):
            raise TypeError("unsupported type for add operation")
        elif self._has_time and not isinstance(other, datetime.datetime):
            other = datetime.datetime.fromordinal(other.toordinal())
        year = (self.year or other.year) + self.years
        month = self.month or other.month
        if self.months:
            assert 1 <= abs(self.months) <= 12
            month += self.months
            if month > 12:
                year += 1
                month -= 12
            elif month < 1:
                year -= 1
                month += 12
        day = min(calendar.monthrange(year, month)[1],
                  self.day or other.day)
        repl = {"year": year, "month": month, "day": day}
        for attr in ["hour", "minute", "second", "microsecond"]:
            value = getattr(self, attr)
            if value is not None:
                repl[attr] = value
        days = self.days
        if self.leapdays and month > 2 and calendar.isleap(year):
            days += self.leapdays
        ret = (other.replace(**repl)
               + datetime.timedelta(days=days,
                                    hours=self.hours,
                                    minutes=self.minutes,
                                    seconds=self.seconds,
                                    microseconds=self.microseconds))
        if self.weekday:
            weekday, nth = self.weekday.weekday, self.weekday.n or 1
            jumpdays = (abs(nth) - 1) * 7
            if nth > 0:
                jumpdays += (7 - ret.weekday() + weekday) % 7
            else:
                jumpdays += (ret.weekday() - weekday) % 7
                jumpdays *= -1
            ret += datetime.timedelta(days=jumpdays)
        return ret