python 时间操作

年华似水，匆匆而过，整理一下这段时间的代码

class TimeClass:
    def __init__(self):
        self.time_handler = datetime.datetime.now(tz="utc")

    def get_now_time(self, time_format):
        """
        get the now time
        :param time_format: "YY-MM-dd"
        :return:
        """
        return self.time_handler.strftime(time_format)

    def get_time_fragment(self, ret_flag):
        if ret_flag in "year":
            return self.time_handle.year
        elif ret_flag in "month":
            return self.time_handle.month
        elif ret_flag in "day":
            return self.time_handle.day
        elif ret_flag in "hour":
            return self.time_handle.hour
        elif ret_flag in "minute":
            return self.time_handle.minute
        elif ret_flag in "second":
            return self.time_handle.second
    @staticmethod
    def get_interval_day_time(day, time_format):
        return_time = datetime.timedelta(day)+datetime.datetime.now()
        return return_time.strftime(time_format)
    @staticmethod
    def get_interval_minutes_time(minutes,time_format):
        return  (datetime.datetime.now()+datetime.timedelta(minutes=minutes)).strftime(time_format)

    def get_interval_minutes_utc_time(self,minutes,time_format):
        return (datetime.datetime.utcnow()+datetime.timedelta(minutes=minutes)).strftime(time_format)

    def get_week_is_day(self):
        return self.time_handle.weekday()

    def str_transform_datetime(self,src_str,time_format):
        return datetime.datetime.strptime(src_str,time_format)

    def utc_switch_cst(self, src_time, ifornotdifferenceutc, time_format='%Y-%m-%d %H:%M:%S'):
        cst_time = datetime.datetime.now()
        utc_time = datetime.datetime.utcnow()
        utc_cst_difference = cst_time-utc_time
        src_time = datetime.datetime.strptime(src_time, time_format)
        if 'utc' == ifornotdifferenceutc:
            return (src_time - utc_cst_difference).strftime(time_format)
        elif 'cst' == ifornotdifferenceutc:
            return (src_time+utc_cst_difference).strftime(time_format)