学习Python后，就想着自己能够做一些小玩意来实践一下学习效果。下面是简单的爬虫实现。

目标：
1.抓取糗事百科的段子
2.将段子保存到本地文件
我们首先先分析糗事百科的页面

Paste_Image.png

每个段子都是以author clearfix开始，下面的div分别是内容，用户名，点赞数等。今天这个例子中获取用户名，内容以及点赞数。从html文件中获取这些信息就要用到正则表达式了，python中提供了RE库完美解决了这个问题。

pattern = re.compile('<div class="author.*?>.*?<h2>(.*?)</h2>.*?<span>(.*?)</span>.*?<span class="stats.*? class="number">(.*?)</i>',re.S)
items = re.findall(pattern, respone.text)

上面这段代码就是从html文件中解析我们所需要的内容。(.*?)是一个group，就是我们需要保存的内容。

获取页面的话用requests就可以了。下面是部分代码。

import re
import requests
# url = "http://www.qiushibaike.com/hot/"
url = "http://www.qiushibaike.com/8hr/page/2/?s=4975313"
session = requests.session()
agent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/57.0.2987.133 Safari/537.36"
host = "www.qiushibaike.com"
headers = {
    'Host':host,
    'User-Agent':agent
}

respone = session.get(url)
pattern = re.compile('<div class="author.*?>.*?<h2>(.*?)</h2>.*?<span>(.*?)</span>.*?<span class="stats.*? class="number">(.*?)</i>',re.S)
items = re.findall(pattern, respone.text)
for item in items:
    print("author="+ item[0]+ "\n" + "articl="+ item[1] + "\n" + "vote=" + item[2])

完整代码：

import re
import requests
import time
import random
class QSBK:
    def __init__(self):
        self.pageIndex = 1
        self.user_agent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/57.0.2987.133 Safari/537.36"
        self.host = url = "http://www.qiushibaike.com/8hr/page/"+str(pageIndex) +"/?s=4975313"
        self.headers = {
            'Host':self.host,
            'User-Agent':self.user_agent
        }
        self.stories = []
        self.session = requests.session()
        self.enable = False

    def getPage(self,pageIndex):
        url = "http://www.qiushibaike.com/"
              # + str(random.randint(100000,999999))
        try:
            resopne = self.session.get(url)
            if resopne.text:
                return resopne.text
        except:
            print("network wrong")

    def getPageItems(self, pageIndex):
        pageStories = []
        pageCode = self.getPage(pageIndex)
        if not pageCode:
            print("获取页面失败！")
        pattern = re.compile('<div class="author.*?>.*?<h2>(.*?)</h2>.*?<span>(.*?)</span>.*?<span class="stats.*? class="number">(.*?)</i>',re.S)
        items = re.findall(pattern, pageCode)
        for item in items:
            pageStories.append([item[0], item[1], item[2]])
        return pageStories

    # 加载并提取页面的内容，加入到列表中
    def loadPage(self):
        # 如果当前未看的页数少于2页，则加载新一页
        if self.enable == True:
            if len(self.stories) < 2:
                # 获取新一页
                pageStories = self.getPageItems(self.pageIndex)
                # 将该页的段子存放到全局list中
                if pageStories:
                    self.stories.append(pageStories)
                    # 获取完之后页码索引加一，表示下次读取下一页
                    self.pageIndex += 1

    def getOneStoty(self, pageStories, page):
        for story in pageStories:
            game = input()
            self.loadPage()
            if game =="Q":
                self.enable = False
                return
            #将段子保存到文件，write中a参数表示文件中增加内容
            try:
                f = open('qsbks.txt','a')
                f.write(story[0] + '\n' + story[1] + '\n' + story[2]+'\n\n')
            finally:
                f.close()
            print("第%s页\t发布人:%s\t\n%s\n赞：%s" %(page, story[0],story[1], story[2]))

    def start(self):
        print("正在读取糗事百科")
        self.enable = True
        self.loadPage()
        nowPage = 0
        while self.enable:
            if len(self.stories) > 0:
                pageStories = self.stories[0]
                nowPage+=1
                del self.stories[0]
                self.getOneStoty(pageStories, nowPage)



spider = QSBK()
spider.start()