python extract daily/hourly balance from a csv file

I have a long file which in particular have these two columns

   Balance     Time
   1000.01     2015-08-23 19:53:23
   1235.21     2015-08-23 17:32:42
    235.21     2015-08-22 17:32:42

I can do some analysis with sqlite but I'm not able to write on a list/vector the last balance of the day (eventually the hour HH:59:59) for all the rows. Do you have an idea how to acheive it?