Python 爬虫工具

• requests

  $ pip install requests
  
  import requests
  
  kw = {'wd':'长城'}
  
  headers = {"User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.99 Safari/537.36"}
  
  formdata = {
      "type":"AUTO",
      "i":"i love python",
      "doctype":"json",
      "xmlVersion":"1.8",
      "keyfrom":"fanyi.web",
      "ue":"UTF-8",
      "action":"FY_BY_ENTER",
      "typoResult":"true"
  }
  
  url = "http://www.baidu.com/s?"
  
  # params 接收一个字典或者字符串的查询参数，字典类型自动转换为url编码，不需要urlencode()
  resp = requests.get(url, params = kw, headers = headers)
  resp = requests.post(url, data = fordata)
  
  # 编码方式
  resp.encoding = 'utf-8'
  
  # 查看响应内容，response.text 返回的是Unicode格式的数据
  print response.text
  
  # 查看响应内容，response.content返回的字节流数据
  print respones.content
  
  
  

• re 正则表达式

  import re
  
  # re.compile 预编译正则表达式
  # .*? 匹配任意长度字符串   (?P<name>.*?) name为变量名，用于提取匹配内容
  # re.S 匹配包括换行符在内的任意字符
  obj = re.compile(r'<li>.*?<span class="title">(?P<name>.*?)</span>'，re.S)
  
  # obj.search 搜索符合正则规则的字符串  group("pic_url")返回一个包含"pic_url"的元组
  result = obj.search(resp.text).group("pic_url")
  
  #字符串中找到正则表达式所匹配的所有子串，并把它们作为一个迭代器返回
  re.finditer(pattern, string, flags=0)
  
  

• xpath 查找HTML标签

  $ pip3 install lxml
  
  from lxml import etree
  
  # resp.text 网页文本
  et = etree.HTML(resp.text)
  
  # 查找<ul>标签 含有class='pic' 的文本内容
  result = et.xpath("//ul[@class='pic']/text()")
  
  # 查找<a>标签 包含的链接
  result = et.xpath("//a/@href")
  
  

• 线程池

  from concurrent.futures import ThreadPoolExecutor
  
  # 最多 10 线程 
  with ThreadPoolExecutor(10) as t:
      t.submit(func,arge)