Python爬蟲(十八)_多線程糗事百科案例
阿新 • • 發佈:2017-12-21
.json afa 安全 rip down 退出 交互 encode tar
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
對於資源,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
- 初始化:class Queue.Queue(maxsize)FIFO先進先出
- 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
- 創建一個"隊列"對象
- import Queue
- myqueue = Queue.Queue(maxsize=10)
- 將一個值放入隊列中
- myqueue.put(10)
- 將一個值從隊列中取出
- myqueue.get()
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()方法從隊頭刪除並返回一個項目。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()
Python爬蟲(十八)_多線程糗事百科案例