class TraceManagerBase(object):
    dblocation = ""
    def __init__(self):
        self.init()

    def init(self):
        self.dblocation = os.path.join(os.path.join(os.path.abspath(os.path.dirname(__file__) + os.path.sep + ".."), "data","traceCoords")) #  os.getcwd(),"data","traceCoords"
        if not os.path.exists(self.dblocation):
            os.makedirs(self.dblocation)

    #從檔案末尾向前讀取，逆序
    def get1(self,sn,n):
        filename = "%s.txt" % sn
        path = os.path.join(self.dblocation, filename)
        data = []
        with open(path,'r') as fs:
            for i in range(n+1):
                if i>0:
                    fs.seek(-113*i,2) #113為每行文字的長度，包含\r\n
                    data.append(fs.readline())
                    print fs.tell()
            #讀取後幾條
            # fs.seek(-113*n,2)
            # print fs.tell()
            # data.append(fs.readlines())
            # print fs.tell()
            print data