code: def doRollover(self):
          
          self.stream.close()
          try:
              if self.backupCount > 0:
                  tmp_location = "%s.0" % self.baseFilename
                  os.rename(self.baseFilename, tmp_location)
                  for i in range(self.backupCount - 1, 0, -1):
                      sfn = "%s.%d" % (self.baseFilename, i)
                      dfn = "%s.%d" % (self.baseFilename, i + 1)
                      if os.path.exists(sfn):
                          if os.path.exists(dfn):
                              os.remove(dfn)
                          os.rename(sfn, dfn)
                  dfn = self.baseFilename + ".1"
                  if os.path.exists(dfn):
                      os.remove(dfn)
                  os.rename(tmp_location, dfn)
          except Exception:
              pass
          finally:
              self.stream = WindowsFile(self.baseFilename, "a", self.encoding)
docs: Do a rollover, as described in __init__().