offsets.py 文件源码

def apply(self, other):
        n = self.n
        # First move to month offset
        cur_mend = self.m_offset.rollforward(other)
        # Find this custom month offset
        cur_cmend = self.cbday.rollback(cur_mend)

        # handle zero case. arbitrarily rollforward
        if n == 0 and other != cur_cmend:
            n += 1

        if other < cur_cmend and n >= 1:
            n -= 1
        elif other > cur_cmend and n <= -1:
            n += 1

        new = cur_mend + n * self.m_offset
        result = self.cbday.rollback(new)
        return result