interrupt.py

 try:
  start_time = datetime.now()
  #do something endlessly
  while True:
   print(datetime.now())
   time.sleep(1)
 # until interrupted by the keyboard  
 except KeyboardInterrupt:
  #behave gracefully in case of interruption
  time_lapsed = (datetime.now() - start_time)
  print('Time elapsed (hh:mm:ss.ms) {}'.format(time_lapsed))