title: Parsing datetime strings containing nanoseconds
body: <p>I have some log files with times in the format HH:MM::SS.nano_seconds (e.g. 01:02:03.123456789). I would like to create a datetime in python so I can neatly do math on the time (e.g. take time differences). strptime works well for <em>microseconds</em> using %f. Do the Python datetime and time modules really not support nanoseconds?</p>