多線程糗事百科案例

案例要求參考上一個糗事百科單進程案例:http://www.cnblogs.com/miqi1992/p/8081929.html

Queue(隊列對象)

Queue是python中的標準庫，可以直接import Queue引用；隊列時線程間最常用的交互數據的形式。

python下多線程的思考
對于資源，加鎖是個重要的環節。因為python原生的list,dict等，都是not thread safe的。而Queue,是線程安全的，因此在滿足使用條件下，建議使用隊列

1. 初始化：class Queue.Queue(maxsize)FIFO先進先出

2. 包中的常用方法：

   • Queue.qszie()返回隊列的大小
   • Queue.empty()如果隊列為空，返回True，否則返回False
   • Queue.full()如果隊列滿了，返回True,反之False
   • Queue.full 與 maxsize大小對應
   • Queue.get([block[, timeout]])獲取隊列，timeout等待事件

3. 創建一個"隊列"對象

   • import Queue
   • myqueue = Queue.Queue(maxsize=10)

4. 將一個值放入隊列中

   • myqueue.put(10)

5. 將一個值從隊列中取出

   • myqueue.get()

多線程示意圖

多線程示意圖

#-*- coding:utf-8 -*-

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

class Thread_crawl(threading.Thread):
    """
        抓取線程類
    """
    def __init__(self, threadID, q):
        threading.Thread.__init__(self)
        self.threadID = threadID
        self.q = q

    def run(self):
        print("String: "+self.threadID)
        self.qiushi_spider()
        print("Exiting: "+self.threadID)

    def qiushi_spider(self):
        while True:
            if self.q.empty():
                break
            else:
                page = self.q.get()
                print('qiushi_spider=', self.threadID, 'page=', str(page))
                url = 'http://www.qiushibaike.com/8hr/page/' + str(page)+"/"
                headers = {
                    'User-Agent':'Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/52.0.2743.116 Safari/537.36',
                    'Accept-Language':'zh-CN,zh;q=0.8'
                }

                #多次嘗試失敗結束，防止死循環
                timeout = 4
                while timeout > 0:
                    timeout -= 1
                    try:
                        content = requests.get(url, headers = headers)
                        data_queue.put(content.text)
                        break
                    except Exception, e:
                        print "qiushi_spider", e
                if timeout < 0:
                    print 'timeout', url



class Thread_Parser(threading.Thread):
    """
        頁面解析類
    """
    def __init__(self, threadID, queue, lock, f):
        threading.Thread.__init__(self)
        self.threadID = threadID
        self.queue = queue
        self.lock = lock
        self.f = f

    def run(self):
        print("starting ", self.threadID)
        global total, exitFlag_Parser
        while not exitFlag_Parser:
            try:
                """
                    調用隊列對象的get()方法從隊頭刪除并返回一個項目。可選參數為block， 默認為True
                    如果隊列為空且block為True，get()就使調用線程暫停，直至有項目可用
                    如果隊列為空且block為False,隊列將引發Empty異常
                """
                item = self.queue.get(False)
                if not item:
                    pass
                self.parse_data(item)
                self.queue.task_done()
                print("Thread_Parser=", self.threadID, 'total=', total)
            except:
                pass
        print "Exiting ", self.threadID

    def parse_data(self, item):
        """
            解析網頁函數
            :param item:網頁內容
            :return
        """
        global total
        try:
            html = etree.HTML(item)
            result = html.xpath('//div[contains(@id,"qiushi_tag")]')
            for site in result:
                try:
                    imgUrl = site.xpath('.//img/@src')[0]
                    title = site.xpath('.//h2')[0].text
                    content = site.xpath('.//div[@class="content"]/span')[0].text.strip()
                    vote = None
                    comments = None
                    try:
                        # 投票次數
                        vote = site.xpath('.//i')[0].text
                        # print(vote)
                        #print site.xpath('.//*[@class="number"]')[0].text
                        # 評論信息
                        comments = site.xpath('.//i')[1].text
                    except:
                        pass
                    result = {
                        'imageUrl' : imgUrl,
                        'title' : title,
                        'content' : content,
                        'vote' : vote,
                        'comments' : comments

                    }

                    with self.lock:
                        self.f.write(json.dumps(result, ensure_ascii=False).encode('utf-8') + '\n') 
                except Exception, e:
                    print("site in result ", e)
        except Exception, e:
            print("parse_data", e)
        with self.lock:
            total += 1


data_queue = Queue()
exitFlag_Parser = False
lock = threading.Lock()
total = 0

def main():
    output = open('qiushibaike.json', 'a')
    #初始化網頁頁碼page從1-10個頁面
    pageQueue = Queue(10)
    for page in range(1, 11):
        pageQueue.put(page)

    #初始化采集線程
    crawlthreads = []
    crawllist = ["crawl-1", "crawl-2", "crawl-3"]

    for threadID in crawllist:
        thread = Thread_crawl(threadID, pageQueue)
        thread.start()
        crawlthreads.append(thread)

    # #初始化解析線程parseList
    parserthreads = []
    parserList = ["parser-1", "parser-2", "parser-3"]

    #分別啟動parserList
    for threadID in parserList:
        thread = Thread_Parser(threadID, data_queue, lock, output)
        thread.start()
        parserthreads.append(thread)

    # 等待隊列情況
    while not pageQueue.empty():
        pass

    #等待所有線程完成
    for t in crawlthreads:
        t.join()
    while not data_queue.empty():
        pass

    #通知線程退出
    global exitFlag_Parser
    exitFlag_Parser = True

    for t in parserthreads:
        t.join()
    print 'Exiting Main Thread'
    with lock:
        output.close()

if __name__ == '__main__':
    main()

多線程糗事百科