offsets.py 文件源码

def apply(self, other):
        def _increment(date):
            if date.month == self.month:
                _, days_in_month = tslib.monthrange(date.year, self.month)
                if date.day != days_in_month:
                    year = date.year
                else:
                    year = date.year + 1
            elif date.month < self.month:
                year = date.year
            else:
                year = date.year + 1
            _, days_in_month = tslib.monthrange(year, self.month)
            return datetime(year, self.month, days_in_month,
                            date.hour, date.minute, date.second,
                            date.microsecond)

        def _decrement(date):
            year = date.year if date.month > self.month else date.year - 1
            _, days_in_month = tslib.monthrange(year, self.month)
            return datetime(year, self.month, days_in_month,
                            date.hour, date.minute, date.second,
                            date.microsecond)

        def _rollf(date):
            if date.month != self.month or\
               date.day < tslib.monthrange(date.year, date.month)[1]:
                date = _increment(date)
            return date

        n = self.n
        result = other
        if n > 0:
            while n > 0:
                result = _increment(result)
                n -= 1
        elif n < 0:
            while n < 0:
                result = _decrement(result)
                n += 1
        else:
            # n == 0, roll forward
            result = _rollf(result)
        return result