學習爬蟲，其樂無窮！
今天給大家帶來一個爬蟲案例，爬取糗事百科搞笑內涵段子，
爬取糗事百科段?，假設??的 URL 是：http://www.qiushibaike.com/8hr/page/1
一、爬取要求：
- 使?requests 獲取??資訊，?XPath / re 做資料提取，
- 獲取每個帖??的 ?戶頭像鏈接 、 ?戶姓名 、 段?內容 、 點贊次數 和 評論次數，
- 保存到 json ?件內，
二、先來看看單執行緒案例
參考代碼：
#qiushibaike.py #import urllib #import re #import chardet import requests from lxml import etree page = 1 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'} try: response = requests.get(url, headers=headers) 167 resHtml = response.text html = etree.HTML(resHtml) result = html.xpath('//div[contains(@id,"qiushi_tag")]') for site in result: item = {} imgUrl = site.xpath('./div/a/img/@src')[0].encode('utf-8') username = site.xpath('./div/a/@title')[0].encode('utf-8') #username = site.xpath('.//h2')[0].text content = site.xpath('.//div[@]/span')[0].te xt.strip().encode('utf-8') # 投票次數 vote = site.xpath('.//i')[0].text #print site.xpath('.//*[@]')[0].text # 評論資訊 comments = site.xpath('.//i')[1].text print imgUrl, username, content, vote, comments except Exception, e: print e
演示效果：
三、多執行緒案例
Queue（佇列物件）：
Queue 是 python 中的標準庫，可以直接 import Queue 引?;佇列是執行緒間最常?的交換資料的形式python 下多執行緒的思考 對于資源，加鎖是個重要的環節，因為 python 原?的list,dict 等，都是 not thread safe 的，?Queue，是執行緒安全的，因此在滿?使?條件下，建議使?佇列，
- 初始化： class Queue.Queue(maxsize) FIFO 先進先出
- 包中的常??法:
Queue.qsize() 回傳佇列的??
Queue.empty() 如果佇列為空，回傳 True,反之 False
Queue.full() 如果佇列滿了，回傳 True,反之 False
Queue.full 與 maxsize ??對應
Queue.get([block[, timeout]])獲取佇列，timeout 等待時間
- 創建?個“佇列”物件import Queue myqueue = Queue.Queue(maxsize = 10)
- 將?個值放?佇列中myqueue.put(10)
- 將?個值從佇列中取出myqueue.get()
多執行緒示意圖：
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參考代碼：
# -*- coding:utf-8 -*- import requests from lxml import etree from Queue import Queue import threading import time import json class thread_crawl(threading.Thread): ''' 抓取執行緒類 ''' def init (self, threadID, q): threading.Thread. init (self) self.threadID = threadID self.q = q def run(self): print "Starting " + self.threadID self.qiushi_spider() print "Exiting ", self.threadID def qiushi_spider(self): # page = 1 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/hot/page/' + str( page) + '/' headers = { 'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; WO W64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/52.0.2743.116 Sa fari/537.36', 'Accept-Language': 'zh-CN,zh;q=0.8'} # 多次嘗試失敗結束、防?死回圈 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): ''' ??決議類； ''' 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?佇列物件的 get()?法從隊頭洗掉并回傳?個項?，可選參 數 為 block，默認為 True， 如果佇列為空且 block 為 True，get()就使調?執行緒暫停，直? 有項?可?， otal 如果佇列為空且 block 為 False，佇列將引發 Empty 例外， ''' item = self.queue.get(False) if not item: pass self.parse_data(item) self.queue.task_done() print 'Thread_Parser=', self.threadID, ',total=', t except: pass print 'Exiting ', self.threadID def parse_data(self, item): ''' 決議??函式 :param item: ??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[@]/ span')[0].text.strip() vote = None comments = None try: vote = site.xpath('.//i')[0].text comments = site.xpath('.//i')[1].text except: pass result = { 'imgUrl': imgUrl, 'title': title, 'content': content, 'vote': vote, 'comments': comments, } with self.lock: # print 'write %s' % json.dumps(result) self.f.write(json.dumps(result, ensure_asci i=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???碼 page 從 1-10 個?? pageQueue = Queue(50) for page in range(1, 11): pageQueue.put(page) #初始化采集執行緒 crawlthreads = [] crawlList = ["crawl-1", "crawl-2", "crawl-3"] for threadID in crawlList: thread = thread_crawl(threadID, pageQueue) thread.start() crawlthreads.append(thread) #初始化決議執行緒 parserList 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) # 等待佇列清空 while not pageQueue.empty(): pass # 等待所有執行緒完成 for t in crawlthreads: t.join() while not data_queue.empty(): pass # 通知執行緒是時候退出 global exitFlag_Parser exitFlag_Parser = True for t in parserthreads: t.join() print "Exiting Main Thread" with lock: output.close() if name == ' main ': main()
四、課后作業
1、爬取筆趣?某部?說的所有頁面，
2、國家?品藥品監督管理總局:http://app1.sfda.gov.cn 采集分類 國產藥品商品名(6994) 下的所有的商品資訊，
這個大家可以試著做一做，如需爬蟲視頻詳解，請點爬蟲視頻，
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標籤：Python