Parse date cleanly, fail if partial

gistfile1.py

def parsedate(datestring, silent=False):
  import dateutil.parser
  import re
  if not datestring: return None
  if re.match('\d{4}-\d{2}-\d{2}', datestring): return datestring
  info=dateutil.parser.parserinfo(dayfirst=True)
  value=dateutil.parser.parser(info)._parse(datestring)
  if value==None: return None
  retval=[value.year, value.month, value.day]
  nones = retval.count(None)
  if nones==3:
    return None
  if nones==0:
    return u"%04d-%02d-%02d"%(retval[0], retval[1], retval[2])
  if not silent: 
    raise AttributeError, "Partial date: %s"%datestring
  return None