爬虫实例01：多线程爬取糗事百科

练习：threading/queue/Lock/xpath

#!/usr/bin/env python
# -*- coding:utf-8 -*-

# 使用了线程库
import threading
# 队列
from queue import Queue
# 解析库
from lxml import etree
# 请求处理
import requests
# json处理
import json
import time

class ThreadCrawl(threading.Thread):
    def __init__(self, threadName, pageQueue, dataQueue):
        #threading.Thread.__init__(self)
        # 调用父类初始化方法
        super(ThreadCrawl, self).__init__()
        # 线程名
        self.threadName = threadName
        # 页码队列
        self.pageQueue = pageQueue
        # 数据队列
        self.dataQueue = dataQueue
        # 请求报头
        self.headers = {'User-Agent':'Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/60.0.3112.101 Safari/537.36'}

    def run(self):
        print("启动 " + self.threadName)
        while not CRAWL_EXIT:
            try:
                # 取出一个数字，先进先出
                # 可选参数block，默认值为True
                #1. 如果对列为空，block为True的话，不会结束，会进入阻塞状态，直到队列有新的数据
                #2. 如果队列为空，block为False的话，就弹出一个Queue.empty()异常，
                page = self.pageQueue.get(False)
                url = "https://www.qiushibaike.com/8hr/page/" + str(page) +"/"
                #print url
                content = requests.get(url, headers = self.headers).text
                time.sleep(1)
                self.dataQueue.put(content)
                #print len(content)
            except:
                pass
        print("结束 " + self.threadName)

class ThreadParse(threading.Thread):
    def __init__(self, threadName, dataQueue, filename, lock):
        super(ThreadParse, self).__init__()
        # 线程名
        self.threadName = threadName
        # 数据队列
        self.dataQueue = dataQueue
        # 保存解析后数据的文件名
        self.filename = filename
        # 锁
        self.lock = lock

    def run(self):
        print("启动" + self.threadName)
        while not PARSE_EXIT:
            try:
                html = self.dataQueue.get(False)
                self.parse(html)
            except:
                pass
        print("退出" + self.threadName)

    def parse(self, html):
        # 解析为HTML DOM
        tree = etree.HTML(html)
        node_list = tree.xpath('//div[contains(@id, "qiushi_tag")]')
        #id属性中包含'qiushi_tag'
        #<div class="article block untagged mb15 typs_long" id="qiushi_tag_120321510">
        for node in node_list:
            author = node.xpath('./div/a[2]/h2')[0].text.strip()
            content = node.xpath('.//div[@class="content"]/span')[0].text.strip()
            zan = node.xpath('.//div[@class="stats"]/span[1]/i')[0].text
            comments = node.xpath('.//a[@class="qiushi_comments"]/i')[0].text
            items = {"author" : author, "content" : content, "zan" : zan, "comments" : comments}

            # with 后面有两个必须执行的操作：__enter__ 和 _exit__
            # 不管里面的操作结果如何，都会执行打开、关闭
            # 打开锁、处理内容、释放锁
            with self.lock:
                self.filename.write(json.dumps(items, ensure_ascii = False)+ "\n")#.encode("utf-8") + "\n")

CRAWL_EXIT = False
PARSE_EXIT = False


def main():
    # 页码的队列，表示20个页面
    pageQueue = Queue(10)
    # 放入1~10的数字，先进先出
    for i in range(1, 11):
        pageQueue.put(i)

    # 采集结果(每页的HTML源码)的数据队列，参数为空表示不限制
    dataQueue = Queue()

    filename = open("duanzi.json", "a")
    # 创建锁
    lock = threading.Lock()

    # 三个采集线程的名字
    crawlList = ["采集线程1号", "采集线程2号", "采集线程3号"]
    # 存储三个采集线程的列表集合
    threadcrawl = []
    for threadName in crawlList:
        thread = ThreadCrawl(threadName, pageQueue, dataQueue)
        thread.start()
        threadcrawl.append(thread)


    # 三个解析线程的名字
    parseList = ["解析线程1号","解析线程2号","解析线程3号"]
    # 存储三个解析线程
    threadparse = []
    for threadName in parseList:
        thread = ThreadParse(threadName, dataQueue, filename, lock)
        thread.start()
        threadparse.append(thread)

    # 等待pageQueue队列为空，也就是等待之前的操作执行完毕
    while not pageQueue.empty():
        pass

    # 如果pageQueue为空，采集线程退出循环
    global CRAWL_EXIT
    CRAWL_EXIT = True

    print("pageQueue为空")

    for thread in threadcrawl:
        thread.join()
        print("1")

    while not dataQueue.empty():
        pass

    global PARSE_EXIT
    PARSE_EXIT = True

    for thread in threadparse:
        thread.join()
        print("2")

    with lock:
        # 关闭文件
        filename.close()
    print("谢谢使用！")

if __name__ == "__main__":
    main()