网络错误时异步FTP上载（Python）

Question

我的Raspberry Pi位于远程位置（通过WIFI加密狗连接互联网），互联网连接不是恒定的

我编写了一个python程序，将传感器读取数据上传到FTP服务器（已完成）

文件将每隔15分钟上传一次（互联网正常工作时）

我的要求

我想在internet不工作时对文件排队，在internet连接恢复时立即发送所有文件。请帮帮我。我在下面附上了我的代码

from time import sleep
import ftplib
import threading
try:
    # for python3
    import queue
    from urllib.request import urlopen
except:
    # for python2 
    import Queue as queue
    from urllib2 import urlopen

class SensorReader():
    #Initialize
    def __init__(self,FTPURL,FTPUN,FTPPas):
        self.FTPURL = FTPURL
        self.FTPUserName = FTPUN
        self.FTPPassword = FTPPas

    #Data as FTPUpload using thread
    def FTPThread(self, fName):
        #Upload text file to FTP
        FTPUp= threading.Thread(target=self.FTPUpload, args=(fName,))
        FTPUp.start()

    #Check if internet working
    def internet_on(self):
        for timeout in [1,5,10,15,60,90,120,150,180]:
            try:
                response=urllib2.urlopen('http://google.com',timeout=timeout)
                return True
            except urllib2.URLError as err: pass
        return False

    #Upload file to FTP
    def FTPUpload(self, file):
        #check if the internet
        if self.internet_on:
            try:
                print(self.FTPURL)
                ftp = ftplib.FTP(self.FTPURL)
                ftp.login(self.FTPUserName, self.FTPPassword)
                ftp.cwd('/')
                ftp.storlines("STOR " + file, open(file, 'rb'))
            except Exception as exc:
                print(exc)
                pass

if __name__ == "__main__":
    FTPURL = ''
    FTPUN = ''
    FTPPas = ''
    m = SensorReader(FTPURL,FTPUN,FTPPas)
    fName = 'SensorRead.txt'
    m.FTPThread(fName)