在爬虫的过程中如何使用Redis的Bloomfilter去重

# encoding=utf-8import redisfrom hashlib import md5class SimpleHash(object):
    def __init__(self, cap, seed):
        self.cap = cap
        self.seed = seed    def hash(self, value):
        ret = 0
        for i in range(len(value)):
            ret += self.seed * ret + ord(value[i])        return (self.cap - 1) & retclass BloomFilter(object):
    def __init__(self, host='localhost', port=6379, db=0, blockNum=1, key='bloomfilter'):
        """
        :param host: the host of Redis
        :param port: the port of Redis
        :param db: witch db in Redis
        :param blockNum: one blockNum for about 90,000,000; if you have more strings for filtering, increase it.
        :param key: the key's name in Redis
        """
        self.server = redis.Redis(host=host, port=port, db=db)
        self.bit_size = 1 << 31  # Redis的String类型最大容量为512M，现使用256M
        self.seeds = [5, 7, 11, 13, 31, 37, 61]
        self.key = key
        self.blockNum = blockNum
        self.hashfunc = []        for seed in self.seeds:
            self.hashfunc.append(SimpleHash(self.bit_size, seed))    def isContains(self, str_input):
        if not str_input:            return False
        m5 = md5()
        m5.update(str_input)
        str_input = m5.hexdigest()
        ret = True
        name = self.key + str(int(str_input[0:2], 16) % self.blockNum)        for f in self.hashfunc:
            loc = f.hash(str_input)
            ret = ret & self.server.getbit(name, loc)        return ret    def insert(self, str_input):
        m5 = md5()
        m5.update(str_input)
        str_input = m5.hexdigest()
        name = self.key + str(int(str_input[0:2], 16) % self.blockNum)        for f in self.hashfunc:
            loc = f.hash(str_input)
            self.server.setbit(name, loc, 1)if __name__ == &#39;__main__&#39;:""" 第一次运行时会显示 not exists!，之后再运行会显示 exists! """
    bf = BloomFilter()    if bf.isContains(&#39;http://www.baidu.com&#39;):   # 判断字符串是否存在
        print &#39;exists!&#39;
    else:        print &#39;not exists!&#39;
        bf.insert(&#39;http://www.baidu.com&#39;)