calculates the time difference between the log lines and writes the 'next' line with the prefixed time lapse

loglapse.py

## calculates the time difference between the log lines
## and writes the 'next' line with the prefixed time lapse
## use: python3 logplapse.py some.log > ts.log
from datetime import datetime
import re
import sys

FMT = '%Y-%m-%d %H:%M:%S'
TS_REGEXP = '\[([0-9:\- ]+)\]'
SPACER = "| ".rjust(10)

if __name__ == '__main__':

    last_ts = None
    total_seconds = 0

    with open(sys.argv[1], "r") as f:
        for line in f:
            rline = line.rstrip()
            m = re.search(TS_REGEXP, line)
            if m == None:
                print(rline)
                continue

            try:
                new_ts = datetime.strptime(m.group(1), FMT)
            except ValueError as err:
                print(rline)
                continue

            if last_ts != None:
                ts = new_ts - last_ts
                if(ts.total_seconds()==0):
                    print(SPACER, rline)
                else:
                    total_seconds += ts.total_seconds()
                    print(ts, "| ", rline)
            else:
                print(SPACER, rline)

            last_ts = new_ts
            
    print("Total seconds: ", total_seconds)