Calculating time differences in python

Recently I had a situation where I need to calculate the timer efficiency.
I have a C++ timer that calls my function after every 5 sec. My function does some critical operation and logs one statement to syslog.
When I observed the logs I found that there is delay in my function execution, slowly the timer started drifting in result and the next function calls are getting delayed !!

So I wanted to calculate how many times the timer has delayed in a day. I grepped for the particular log in my syslog and redirected to a file.

file format is like this:
Jan 29 06:34:24
Jan 29 06:34:29
Jan 29 06:34:34
Jan 29 06:34:39
..
..
Now I should compare the lines in the file and log if the time difference is greater than 5 sec.
compare line 1 with line 2
line 2 with line 3, then line 3 with line 4 and so on...

	#!/usr/bin/python
	from datetime import datetime
	f = open("./timelogs")
	lines = f.readlines()
	for time_list in [lines[i:i+2] for i in range(0, len(lines))]:
	try:
	d1 = datetime.strptime(time_list[0].strip(), "%b %d %H:%M:%S")
	d2 = datetime.strptime(time_list[1].strip(), "%b %d %H:%M:%S")
	td = (d2 - d1) # (d2 - d2).total_seconds() can be used in python 2.7 +
	seconds = float((td.microseconds + (td.seconds + td.days * 24 * 3600) * 10**6)) / 10**6
	if seconds != 5.0 :
	print "time diff is :", seconds, " - ", map(str.strip, time_list)
	except IndexError:
	pass

view raw timediff.py hosted with ❤ by GitHub

Here the bad thing is f.readlines() ... It will load whole file in to list and tried to read 2 lines at a time.
If anybody reads this post :P and if you know any better working solution please share. :)