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 mmf_fft(f, title='', mmfmin=1e-2, ax=0):
    """plot winding mmf harmonics"""
    if ax == 0:
        ax = plt.gca()
    if title:
        ax.set_title(title)
    else:
        ax.set_title('MMF Harmonics')
    ax.grid(True)
    order, mmf = np.array([(n, m) for n, m in zip(f['nue'],
                                                  f['mmf_nue']) if m > mmfmin]).T
    try:
        markerline1, stemlines1, _ = ax.stem(order, mmf, '-.', basefmt=" ",
                                             use_line_collection=True)
        ax.set_xticks(order)
    except ValueError:  # empty sequence
        pass