#!/usr/bin/env python
 
import datetime
import time
 
start_time = datetime.datetime.now()
time.sleep(5)
end_time = datetime.datetime.now()
delta = end_time - start_time
delta_gmtime = time.gmtime(delta.total_seconds())
duration_str = time.strftime("%H:%M:%S", delta_gmtime)
 
print "start time:", start_time
print "end time:", end_time
print "delta_gmtime:", delta_gmtime
print "duration:", duration_str

flying-bird@flyingbird:~/examples/python/time_test$ ./time_test.py 
start time: 2015-06-09 20:11:47.437286
end time: 2015-06-09 20:11:52.440018
delta_gmtime: time.struct_time(tm_year=1970, tm_mon=1, tm_mday=1, tm_hour=0, tm_min=0, tm_sec=5, tm_wday=3, tm_yday=1, tm_isdst=0)
duration: 00:00:05
flying-bird@flyingbird:~/examples/python/time_test$ 

import datetime
import time
 
class TimeDuration(object):
  'Time duration.'
  
  def __init__(self):
    pass
    
  def start(self):
    self.start_time = datetime.datetime.now()
    self.end_time = None
    
  def stop(self):
    if self.start_time is None:
      print "ERROR: start() must be called before stop()."
      return
      
    self.end_time = datetime.datetime.now()
    
  def getDurationStr(self):
    'String of duration with the format "%H:%M:%S".'
    if self.start_time is None or self.end_time is None:
      print "ERROR: start() and stop() must be called first.";
      return
    
    delta = self.end_time - self.start_time
    delta_gmtime = time.gmtime(delta.total_seconds())
    return time.strftime("%H:%M:%S", delta_gmtime)

flying-bird@flyingbird:~/examples/python/time_test$ cat time_test2.py
#!/usr/bin/env python
 
import time
import time_utils
 
duration = time_utils.TimeDuration()
duration.start()
time.sleep(5)
duration.stop()
 
print duration.getDurationStr() 
flying-bird@flyingbird:~/examples/python/time_test$ ./time_test2.py
00:00:05
flying-bird@flyingbird:~/examples/python/time_test$