device_id             time       x        y      z
ghXzbQTyASMwePeQJXQ     00:04:23   1787.4   -2.1   4992.7
                        00:16:51   9757.3   -4.1   4922.0
                        00:25:47   3337.4   -2.2   4132.4
bLXzbQTyASMxeP6QJXQ     00:36:24   6957.2   -1.8   1342.9
                        00:47:20   2956.8   -3.7   7942.8
                                :
                                :

def get_sec(time_str):
    """Get Seconds from time."""
    h, m, s = time_str.split(':')
    return int(h) * 3600 + int(m) * 60 + int(s)

get_sec(DF23[time])

get_sec(DF23.time)

<module 'time' (built-in)>

'DataFrame' object has no attribute 'time'

get_sec(DF23['time'])