output

~$ ./sum_hours.py tracking.txt 
08/02/2012 21:00 23:59 -> 2:59:00 hours
09/02/2012 00:00 00:40 -> 0:40:00 hours
Group hours: 3:39:00

09/02/2012 21:00 23:59 -> 2:59:00 hours
09/02/2012 00:00 01:40 -> 1:40:00 hours
Group hours: 4:39:00

09/02/2012 22:30 23:59 -> 1:29:00 hours
10/02/2012 00:00 01:40 -> 1:40:00 hours
Group hours: 3:09:00

10/02/2012 22:58 23:59 -> 1:01:00 hours
11/02/2012 00:00 05:40 -> 5:40:00 hours
Group hours: 6:41:00

11/02/2012 19:00 23:59 -> 4:59:00 hours
12/02/2012 00:00 04:40 -> 4:40:00 hours
Group hours: 9:39:00

12/02/2012 16:00 18:00 -> 2:00:00 hours
12/02/2012 22:00 23:59 -> 1:59:00 hours
13/02/2012 00:00 02:00 -> 2:00:00 hours
Group hours: 5:59:00

13/02/2012 23:00 23:59 -> 0:59:00 hours
14/02/2012 00:00 00:40 -> 0:40:00 hours
Group hours: 1:39:00

Group hours: 0:00:00

Total hours: 1 day, 11:25:00

sum_hours.py

#!/usr/bin/env python

# from a file with entries like that
# 
# 08/02/2012 09:00 23:59
# 09/02/2012 00:00 00:40
# 
# 09/02/2012 09:00 23:59
# 09/02/2012 00:00 01:40
# 
# 09/02/2012 22:30 23:59
# 10/02/2012 00:00 01:40
# 
# read and get 'worked' ours grouping by non blank lines
# 
# pass file as argument
#
import sys, os
import datetime
from pprint import pprint

def process(tracking_file):

    f = open(os.path.realpath(tracking_file),'r')
    lines = ['\n'] + f.readlines()
    groups = []

    for i,line in enumerate(lines):
        if i == 0 or line == '\n':
            if i != 0:
                groups.append(this_group)
            this_group = []
        else:
            this_group.append(line)

    hours = []
    dformat = '%d/%m/%Y %H:%M'
    for group in groups:
        this_hours = []
        for entry in group:
            date,ini_time,end_time = entry.replace('\n','').split(' ')
            ini_time =datetime.datetime.strptime(date+' '+ini_time,dformat) 
            end_time =datetime.datetime.strptime(date+' '+end_time,dformat) 
            this_hours.append(end_time - ini_time)
            print '%s -> %s hours' % (entry.replace('\n',''),this_hours[-1])
        print 'Group hours: %s' % sum(this_hours,datetime.timedelta())
        print
        hours.append(sum(this_hours,datetime.timedelta()))
    print 'Total hours: %s' % sum(hours,datetime.timedelta())

if __name__ == '__main__':
    try:
        tracking_file = sys.argv[1]
    except IndexError:
        print "Shoud receive a file as parameter!"
        sys.exit(1)

    if os.path.exists(tracking_file) and os.path.isfile(tracking_file):
        process(tracking_file)
    else:
        print "The parameter isn't a file!"
        sys.exit(1)

tracked_hours.txt

08/02/2012 21:00 23:59
09/02/2012 00:00 00:40

09/02/2012 21:00 23:59
09/02/2012 00:00 01:40

09/02/2012 22:30 23:59
10/02/2012 00:00 01:40

10/02/2012 22:58 23:59
11/02/2012 00:00 05:40

11/02/2012 19:00 23:59
12/02/2012 00:00 04:40

12/02/2012 16:00 18:00
12/02/2012 22:00 23:59
13/02/2012 00:00 02:00

13/02/2012 23:00 23:59
14/02/2012 00:00 00:40