def robotsrulesetOfDomain(self, domain):
		'''检查domain是否在数据库中,
			否 --> (False, None)
			是 --> (True, 数据库中存储的robots.txt内容)
		'''
		exist = False
		cur = self.conn.cursor()
		# 是否存在
		cur.execute("SELECT 1 FROM Domains WHERE domain=?", (domain,))
		if cur.fetchone() :
			exist = True
		# 存在的话,结果是什么
		cur.execute("SELECT rules FROM Domains,Rulesets "
			"WHERE domain=? AND Domains.did=Rulesets.did"
			,(domain,) )
		ruleset = cur.fetchone()
		return (exist, ruleset)
def _maybe_name(obj):
  """Returns object name if it has one, or a message otherwise.

  This is useful for names that apper in error messages.
  Args:
    obj: Object to get the name of.
  Returns:
    name, "None", or a "no name" message.
  """
  if obj is None:
    return "None"
  elif hasattr(obj, "name"):
    return obj.name
  else:
    return "<no name for %s>" % type(obj)