太复杂。本人不会

import requests
from lxml import etree
from urllib.parse import urlparse
from time import sleep

from threading import Thread
from queue import Queue
import sys
from redis import Redis
# 用IDLE来记录线程的空闲
IDLE = 0
# 用WORKING来记录线程的工作状态
WORKING = 1

rds  = Redis("127.0.0.1",6379,db=10)

# 定义一个装饰器对象
class retry(object):
    def __init__(self,max_tries=3,wait=3,exceptions=(Exception,)):
        self.max_tries = max_tries
        self.wait = wait
        self.exceptions = exceptions

    def __call__(self, f):
        def wrapper(*args,**kwargs):
            for i in range(self.max_tries+1):
                try:
                    result = f(*args,**kwargs)
                except self.exceptions as e:
                    print("waitting",e)
                    sleep(self.wait) # 如果有异常休眠一会再请求
                    print("retry %s "%(i+1))
                    continue
                else:
                    return result
        return wrapper


# 定义一个集合，用于存放访问过的网址
REQUESTED_URL = set()
# 下载页面
@retry(3,3)
def fetch(url):
    print(f'Fetching: {url}')
    res = requests.get(url)
    # 请求过以后，把网址添加到集合中
    REQUESTED_URL.add(url)
    # 请求成功，把页面内容返回出去
    if res.status_code == 200:
        return res.text
    return None

# 解析数据
def paese(html):
    # 剔除一些无效的url对应的页面
    if html in [None,'',b'']:
        return []
    # 通过xpath语法寻找a标签
    doc = etree.HTML(html)
    if doc is None:
        return []

    # 取当前页面中url
    urls = doc.xpath("//a/@href")

    # print(urls)
    # 对页面上获取到的链接进行清洗
    # 定义一个列表，用于存放清洗完成url
    url_list = []
    for ori_url in urls:
        parse_url = urlparse(ori_url) # ParseResult(scheme='', netloc='', path='/a/249902322_102150', params='', query='_f=m-index_business_news_9', fragment='')
        # print(parse_url)
        # 过滤域名
        domain = parse_url.netloc.strip() or "m.sohu.com"
        if domain == "m.sohu.com":
            # 过滤协议
            scheme = parse_url.scheme.strip() or "http"
            path = parse_url.path.strip()
            query = f'?{parse_url.query}'.strip() if parse_url.query else ''
            # 拼接url
            url = f'{scheme}://{domain}{path}{query}'
            # 把拼接好的url存储
            url_list.append(url)
    return url_list


# 定义一个函数调用下载与解析
def get_and_parse(url,url_queue):
    html = fetch(url)
    # paese(html)
    # print(html)
    for url in paese(html):
        url_queue.put(url)

# #定义一个函数，用于处理线程
# def process(url_list):
#     queue = Queue()
#     workers = []
#     for url in url_list:
#         t = Thread(target=get_and_parse,args=(url,queue))
#         t.setDaemon(True)
#         workers.append(t)
#         t.start()
#     for t in workers:
#         t.join()
#     return list(queue.queue)

# 创建一个多线程爬虫类
class Spider(Thread):
    # def __init__(self,todo_list):
    def __init__(self):
        super().__init__()
        # self.todo_list = todo_list
        self.stat = IDLE

    def is_idle(self):
        return self.stat == IDLE

    def run(self):
        while True:
            url = rds.blpop("TODO_LIST")[1]
            # url = self.todo_list.get()
            # 开始抓取
            self.stat = WORKING
            html = fetch(url)

            # url_list = set(paese(html))
            # url_list -= REQUESTED_URL
            url_list = set([url.encode('utf-8') for url in paese(html)])
            url_list -= rds.smembers("REQUEST_URL") # 去重

            # # 将新得到的url添加到循环里面
            # for url in url_list:
            #     self.todo_list.put(url)
            if url_list:
                rds.lpush("TODO_LIST",*url_list)

            # 把工作状态设置为空闲
            self.stat = IDLE


def main(max_threads):
    # 添加任务
    print("Start")
    # todo_list = Queue() # 待抓取的url
    # todo_list.put("http://m.sohu.com")
    print(rds.lpush("TODO_LIST","http://m.sohu.com/"))
    # 创建n个线程，并启动
    # spiders = [Spider(todo_list) for i in range(max_threads)]
    spiders = [Spider() for i in range(max_threads)]
    for spd in spiders:
        spd.start()

    # 检测所有的线程是否全部完成工作
    while True:
        # 改成redis键的判断
        # if todo_list.empty() and  [spd.is_idle() for spd in spiders]:
        if rds.llen("TODO_LIST")==0 and [spd.is_idle() for spd in spiders]:
            # 当前待抓取的列表为空，所有的线程也全部为空闲，退出程序
            print("所有的工作都完成了")
            sys.exit(0)
        else:
            print("REQUESRED %d" % rds.scard("REQUEST_URL"))
            sleep(1)

if __name__ == '__main__':
    if len(sys.argv) >= 2:
        max_threads = int(sys.argv[1])
        main(max_threads)