lxml与bs4 select、58爬虫实例

• 基础班
  ```
  #coding=utf8
  from future import unicode_literals
  from bs4 import BeautifulSoup
  import requests

  headers={
  'User-Agent':'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.75 Safari/537.36',
  'Cookie':''
  }
  url='http://www.tripadvisor.cn/Hotels-g60763-New_York_City_New_York-Hotels.html'

  wb_data=requests.get(url,headers=headers)
  soup=BeautifulSoup(wb_data.content,'lxml')
  titles=soup.select('a.property_title')
  imgs=soup.select('img[height="200"]')//经过标签的属性height=200获取全部高为200的图片，也能够用class属性获取，如imgs=soup.select('img.photo_image')
  cates=soup.select('div.clickable_tags')
  for title,img,cate in zip(titles,imgs,cates):
  data={
  'title':title.get_text(),//获取标题文本
  'img':img.get('src'),//经过src获取图片
  'cate':cate.get_text(',')//获取文本，中间用“，”隔开
  }
  print(data)
  ```

• 分类实现：
  ```
  from bs4 import BeautifulSoup
  import requests

  headers={
  'User-Agent':'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.75 Safari/537.36',
  'Cookie':''
  }
  url_saves='http://www.tripadvisor.cn/Hotels-g60763-New_York_City_New_York-Hotels.html'

  def get_attractions(url,data=None):
  wb_data=requests.get(url_saves)
  soup=BeautifulSoup(wb_data.text,'lxml')
  soup.decode('utf-8')
  titles=soup.select('a.property_title')
  imgs=soup.select('img.photo_image')
  mates=soup.select('div.clickable_tags')

  for title,img,mate in zip(titles,imgs,mates):
        data={
            'title':title.get_text(),
            'img':img.get('src'),
            'mate':mate.get_text()
        }
        print(data)

  def get_favs(url,data=None):
  wb_data=requests.get(url,headers=headers)
  soup=BeautifulSoup(wb_data.text,'lxml')
  titles=soup.select('a.property_title')
  imgs = soup.select('img.photo_image')
  mates = soup.select('div.clickable_tags')

  if data==None:
        for title, img, mate in zip(titles, imgs, mates):
            data = {
                'title': title.get_text(),
                'img': img.get('src'),
                'mate': mate.get_text()
            }
            print(data)

  get_favs(url_saves)
  ```

• 对于用连接控制页数的网页，获取全部页面的方法：
  urls=['http://tieba.baidu.com/p/4900705159?pn={}',format(str(i)) for i in range(1,6,1)]

  for single_url in urls:
      get_attractions(single_url)//经过循环调用上面代码中的类获取每一页的信息

• 对于用js处理的图片，能够设置User-Agent模拟手机客户端登录，而后获取图片

• 58同城实例

from bs4 import BeautifulSoup
    import requests
    import time
    url='http://bj.58.com/pingbandiannao/24604629984324x.shtml'
    wb_data = requests.get(url)
    soup = BeautifulSoup(wb_data.text,'lxml')
    def get_links_from(who_sells):
        urls = []
        list_view = 'http://bj.58.com/pbdn/{}/pn2/'.format(str(who_sells))
        wb_data = requests.get(list_view)
        soup = BeautifulSoup(wb_data.text,'lxml')
        for link in soup.select('td.t a.t'): //查找td标签下的t和a标签下的t
            urls.append(link.get('href').split('?')[0])
        return urls
    def get_views_from(url):
        id = url.split('/')[-1].strip('x.shtml')  //以/分割连接，而后用-1取最后一个，用strip('x,shtml')在取到的数据后追加x.html
        api = 'http://jst1.58.com/counter?infoid={}'.format(id)//上面的id是动态的，因此用.format加入动态id
        //这个是找到了58的查询接口，不了解接口能够参照一下新浪微博接口的介绍
        js = requests.get(api)
        views = js.text.split('=')[-1] // 找到的id用=号分割，而后返回最后一个
        return views
    def get_item_info(who_sells=0):
        urls = get_links_from(who_sells)
        for url in urls:
            wb_data = requests.get(url)
            soup = BeautifulSoup(wb_data.text,'lxml')
            data = {
                'title':soup.title.text,//直接获取标题文本
                'price':soup.select('.price')[0].text,
                #获取地区，对于没有填写地区的设置为None，使用 .stripped_strings 能够去除多余空格或空行内容
                'area' :list(soup.select('.c_25d')[0].stripped_strings) if soup.find_all('span','c_25d') else None,
                'date' :soup.select('.time')[0].text,
                'cate' :'我的' if who_sells == 0 else '商家',
                # 'views':get_views_from(url)
            }
            print(data)
    get_item_info(url)
    get_links_from(1)
    get_item_info()

• requests自带status检测函数，用于判断页面是否存在

wb_data=requests.get(url)
if wb_data.status_code==404:  //用requests的status_code获取页面的状态码，判断是否为404
    pass

• 线程池

# http://cn-proxy.com/
proxy_list = [
    'http://117.177.250.151:8081',
    'http://111.85.219.250:3129',
    'http://122.70.183.138:8118',
    ]
proxy_ip = random.choice(proxy_list) # 随机获取代理ip
proxies = {'http': proxy_ip}

• 代码解析方法

data = {
            'title':soup.title.text.strip(),
            'price':soup.select('.f22.fc-orange.f-type')[0].text.strip(),
            'pub_date':soup.select('.pr-5')[0].text.strip().split(' ')[0],

            //先用map把数据装入map中，map中lambda表达式定义x，用x的text方法迭代后面soup.select()获取到的数据，从而取出文本，map返回的是一个地址，用list把map转换为值
            'area':list(map(lambda x:x.text,soup.select('ul.det-infor > li:nth-of-type(3) > a'))),
            'cates':list(soup.select('ul.det-infor > li:nth-of-type(1) > span')[0].stripped_strings),
            'url':url
        }

• 用该方法把url去重

db_urls = [item['url'] for item in url_list.find()]
index_urls = [item['url'] for item in item_info.find()]
x = set(db_urls)
y = set(index_urls)
rest_of_urls = x-y