Accurate timestamping in Python logging -

i've been building error logging app , after way of accurately timestamping incoming data. when accurately mean each timestamp should accurate relative each other (no need sync atomic clock or that).

i've been using datetime.now() first stab, isn't perfect:

>>> in range(0,1000): ...     datetime.datetime.now() ... datetime.datetime(2008, 10, 1, 13, 17, 27, 562000) datetime.datetime(2008, 10, 1, 13, 17, 27, 562000) datetime.datetime(2008, 10, 1, 13, 17, 27, 562000) datetime.datetime(2008, 10, 1, 13, 17, 27, 562000) datetime.datetime(2008, 10, 1, 13, 17, 27, 578000) datetime.datetime(2008, 10, 1, 13, 17, 27, 578000) datetime.datetime(2008, 10, 1, 13, 17, 27, 578000) datetime.datetime(2008, 10, 1, 13, 17, 27, 578000) datetime.datetime(2008, 10, 1, 13, 17, 27, 578000) datetime.datetime(2008, 10, 1, 13, 17, 27, 609000) datetime.datetime(2008, 10, 1, 13, 17, 27, 609000) datetime.datetime(2008, 10, 1, 13, 17, 27, 609000) etc. 

the changes between clocks first second of samples looks this:

usecs    difference 562000   578000  16000 609000  31000 625000  16000 640000  15000 656000  16000 687000  31000 703000  16000 718000  15000 750000  32000 765000  15000 781000  16000 796000  15000 828000  32000 843000  15000 859000  16000 890000  31000 906000  16000 921000  15000 937000  16000 968000  31000 984000  16000 

so looks timer data updated every ~15-32ms on machine. problem comes when come analyse data because sorting other timestamp , sorting timestamp again can leave data in wrong order (chronologically). nice have time stamps accurate point call time stamp generator gives unique timestamp.

i had been considering methods involving using time.clock() call added starting datetime, appreciate solution work accurately across threads on same machine. suggestions gratefully received.

you're unlikely sufficiently fine-grained control can eliminate possibility of duplicate timestamps - you'd need resolution smaller time takes generate datetime object. there couple of other approaches might take deal it:

1. deal it. leave timestamps non-unique are, rely on python's sort being stable deal reordering problems. sorting on timestamp first, else retain timestamp ordering - have careful start timestamp ordered list every time, rather doing multiple sorts on same list.

2. append own value enforce uniqueness. eg. include incrementing integer value part of key, or append such value if timestamps different. eg.

the following guarantee unique timestamp values:

    class timestamper(object):         def __init__(self):             self.lock = threading.lock()             self.prev = none             self.count = 0           def gettimestamp(self):              self.lock:                  ts = str(datetime.now())                  if ts == self.prev:                      ts +='.%04d' % self.count                      self.count += 1                  else:                      self.prev = ts                      self.count = 1              return ts 

for multiple processes (rather threads), gets bit trickier though.