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 drawMe(self, g, r):
        self.g = g
        self.r = r
        self.g.save()
        self.g.moveTo(self.x,self.y)
        self.g.beginPath()
        # 根據 r 半徑繪製一個圓代表點的所在位置
        self.g.arc(self.x, self.y, self.r, 0, 2*math.pi, true)
        self.g.moveTo(self.x,self.y)
        self.g.lineTo(self.x+self.r, self.y)
        self.g.moveTo(self.x, self.y)
        self.g.lineTo(self.x-self.r, self.y)
        self.g.moveTo(self.x, self.y)
        self.g.lineTo(self.x, self.y+self.r)
        self.g.moveTo(self.x, self.y)
        self.g.lineTo(self.x, self.y-self.r)
        self.g.restore()
        self.g.stroke()