How to format elapsed time from seconds to hours, minutes, seconds and milliseconds in Python?

You could exploit timedelta:

>>> from datetime import timedelta
>>> str(timedelta(seconds=elapsed))
'0:00:00.233000'

If you want to include times like 0.232999801636 as in your input:

import time
start = time.time()
end = time.time()
hours, rem = divmod(end-start, 3600)
minutes, seconds = divmod(rem, 60)
print("{:0>2}:{:0>2}:{:05.2f}".format(int(hours),int(minutes),seconds))

Example:

In [12]: def timer(start,end):
   ....:         hours, rem = divmod(end-start, 3600)
   ....:         minutes, seconds = divmod(rem, 60)
   ....:         print("{:0>2}:{:0>2}:{:05.2f}".format(int(hours),int(minutes),seconds))
   ....:     

In [13]: timer(12345.242,12356.434)
00:00:11.19
In [14]: timer(12300.242,12600.5452)
00:05:00.30
In [19]: timer(0.343,86500.8743)
24:01:40.53
In [16]: timer(0.343,865000.8743)
 240:16:40.53    
In [17]: timer(0,0.232999801636)
00:00:00.23