用队列方式实现多线程爬虫

Posted 2020-11-29 nuochengze

声明：无意滋生事端，仅学习分享，如有侵权，将立即删除。

说明：糗事百科段子的爬取，采用了队列和多线程的方式，其中关键点是Queue.task_done()、Queue.join()，保证了线程的有序进行。

import requests
from lxml import etree
import json
from queue import Queue
import threading

class Qsbk(object):
    def __init__(self):
        self.headers = {
            "User-Agent": "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (Khtml, like Gecko) Chrome/81.0.4044.138 Safari/537.36",
            "Referer": "https://www.qiushibaike.com/"
        }
        # 实例化三个队列，用来存放内容
        self.url_queue = Queue()
        self.html_queue = Queue()
        self.content_queue = Queue()

    def get_total_url(self):
        """
        获取了所有的页面url，并且返回url_list
        return:url_list
        现在放入url_queue队列中保存
        """
        url_temp = "https://www.qiushibaike.com/text/page/{}/"
        url_list = list()
        for i in range(1,13):
            # url_list.append(url_temp.format(i))
            # 将生成的url放入url_queue队列
            self.url_queue.put(url_temp.format(i))

    def parse_url(self):
        """
        发送请求，获取响应，同时etree处理html
        """
        while self.url_queue.not_empty:
            # 判断非空，为空时结束循环

            # 从队列中取出一个url
            url = self.url_queue.get()
            print("parsing url:",url)
            # 发送请求
            response = requests.get(url,headers=self.headers,timeout=10)
            # 获取html字符串
            html = response.content.decode()
            # 获取element类型的html
            html = etree.HTML(html)
            # 将生成的element对象放入html_queue队列
            self.html_queue.put(html)
            # Queue.task_done() 在完成一项工作之后，Queue.task_done()函数向任务已经完成的队列发送一个信号
            self.url_queue.task_done()

    def get_content(self):
        """
        解析网页内容，获取想要的信息
        """
        while self.html_queue.not_empty:
            items = list()
            html = self.html_queue.get()
            total_div = html.xpath("//div[@class=‘col1 old-style-col1‘]/div")
            for i in total_div:

                author_img = i.xpath(".//a[@rel=‘nofollow‘]/img/@src")
                author_img = "https"+author_img[0] if len(author_img)>0 else None

                author_name = i.xpath(".//a[@rel=‘nofollow‘]/img/@alt")
                author_name = author_name[0] if len(author_name)>0 else None

                author_href = i.xpath("./a/@href")
                author_href = "https://www.qiushibaike.com/"+author_href[0] if len(author_href)>0 else None

                author_gender = i.xpath("./div[1]/div/@class")
                author_gender = author_gender[0].split(" ")[-1].replace("Icon","").strip() if  len(author_gender)>0 else None

                author_age = i.xpath("./div[1]/div/text()")
                author_age = author_age[0] if len(author_age)>0 else None

                content = i.xpath("./a/div/span/text()")
                content = content[0].strip() if len(content)>0 else None

                content_vote = i.xpath("./div[@class=‘stats‘]/span[@class=‘stats-vote‘]/i/text()")
                content_vote = content_vote[0] if len(content_vote)>0 else None

                content_comment_numbers = i.xpath("./div[@class=‘stats‘]/span[@class=‘stats-comments‘]/a/i/text()")
                content_comment_numbers = content_comment_numbers[0] if len(content_comment_numbers)>0 else None

                item = {
                    "author_name":author_name,
                    "author_age" :author_age,
                    "author_gender":author_gender,
                    "author_img":author_img,
                    "author_href":author_href,
                    "content":content,
                    "content_vote":content_vote,
                    "content_comment_numbers":content_comment_numbers,
                }
                items.append(item)
            self.content_queue.put(items)
            # task_done的时候，队列计数减一
            self.html_queue.task_done()

    def save_items(self):
        """
        保存items
        """
        while self.content_queue.not_empty:
            items = self.content_queue.get()
            with open("quishibaike.txt",‘a‘,encoding=‘utf-8‘) as f:
                for i in items:
                    json.dump(i,f,ensure_ascii=False,indent=2)
            self.content_queue.task_done()

    def run(self):
        # 获取url list
        thread_list = list()
        thread_url = threading.Thread(target=self.get_total_url)
        thread_list.append(thread_url)

        # 发送网络请求
        for i in range(10):
            thread_parse = threading.Thread(target=self.parse_url)
            thread_list.append(thread_parse)

        # 提取数据
        thread_get_content = threading.Thread(target=self.get_content)
        thread_list.append(thread_get_content)

        # 保存
        thread_save = threading.Thread(target=self.save_items)
        thread_list.append(thread_save)


        for t in thread_list:
            # 为每个进程设置为后台进程，效果是主进程退出子进程也会退出
            t.setDaemon(True)
            t.start()
        
        # 让主线程等待，所有的队列为空的时候才能退出
        self.url_queue.join()
        self.html_queue.join()
        self.content_queue.join()


if __name__=="__main__":
    obj = Qsbk()
    obj.run()