How to find total work hours by device I'd?

I have a log table: processlogmodel

id      log_time               log_type device_id
1061    1/1/2016 9:08:45    PM  False   2
1062    1/1/2016 11:19:45   PM  False   2
1063    1/2/2016 8:44:46    AM  False   2
1064    1/2/2016 3:56:46    AM  True    3
1065    1/2/2016 12:51:46   AM  True    2
1066    1/1/2016 6:33:46    PM  False   2
1067    1/2/2016 8:20:46    AM  False   3
1068    1/2/2016 7:57:46    AM  True    1
1069    1/1/2016 6:21:46    PM  False   1
1070    1/2/2016 8:34:47    AM  False   2
1071    1/2/2016 12:18:47   AM  True    1
1072    1/1/2016 6:14:47    PM  True    3
1073    1/2/2016 8:21:47    AM  True    2
1074    1/2/2016 12:39:47   AM  False   3
1075    1/1/2016 11:23:47   PM  False   1
1076    1/1/2016 8:02:11    PM  True    1
1078    1/2/2016 4:02:12    AM  False   1
1079    1/1/2016 8:02:11    PM  True    2
1080    1/1/2016 10:02:11   PM  True    2
1081    1/1/2016 4:54:11    AM  False   2
1083    1/1/2016 5:47:11    AM  True    2
1084    1/2/2016 4:47:12    AM  False   2
1085    1/2/2016 8:39:12    AM  True    2

How can I find total work hours by device?

0 means on and 1 means off, I use sqlite3 and Python.

its just log model and i add record with log_type=0 for start working and log_type=1 for end work time for a device. i want to : 1. find continuous record by devices for calculate work duration 2. find total work hours by device.