def log_request(self, handler):
  """Writes a completed HTTP request to the logs.

  By default writes to the python root logger. To change
  this behavior either subclass Application and override this method,
  or pass a function in the application settings dictionary as
  ``log_function``.
  """
  if "log_function" in self.settings:
    self.settings["log_function"](handler)
    return
  if handler.get_status() < 400:
    log_method = access_log.info
  elif handler.get_status() < 500:
    log_method = access_log.warning
  else:
    log_method = access_log.error
  request_time = 1000.0 * handler.request.request_time()
  log_method("%d %s %.2fms", handler.get_status(),
        handler._request_summary(), request_time)

access_log = logging.getLogger(“tornado.access”)

class NoParsingFilter(logging.Filter):
  def filter(self, record):
    if record.name == 'tornado.access' and record.levelno == 20:
      return False
    return True

logobj = logging.getLogger('server')
logobj.addFilter(NoParsingFilter())

#第一个参数是一个返回bool值的一般函数或lambda函数，第二个参数是一个可迭代对象
#最后返回一个可迭代对象，可以通过list获得
def is_positive(item):
  return item>0
values = [1,-2,3,-4]
print(filter(is_poditive,values))
a = list(filter(is_positive,values))
print(a)
print(values)
#output
<filter object at 0x000002398A1AB4A8>
[1, 3]
[1, -2, 3, -4]
b = list(filter(lambda item:item>0,values))
print(b)
 #output 
[1,3]