Python 爬虫知识点

一、基础知识

1、HTML分析

2、urllib爬取

导入urilib包（Python3.5.2）

3、urllib保存网页

import urllib.request
url = "http://www.cnblogs.com/wj204/p/6151070.html"
html = urllib.request.urlopen(url).read()
fh=open("F:/20_Python/3000_Data/2.html","wb")
fh.write(html)
fh.close()

4、模拟浏览器

import urllib.request
url="http://www.cnblogs.com/"
headers=("User-Agent","Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/49.0.2623.22 Safari/537.36 SE 2.X MetaSr 1.0")
opener=urllib.request.build_opener()
opener.addheaders=[headers]
data=opener.open(url).read()
fh=open("F:/20_Python/3000_Data/1.html","wb")
fh.write(data)
fh.close()

5、urllib保存图片

 使用  http://www.bejson.com/  查看存储在JS中的Json数据g_page_config

import re
import urllib.request
keyWord = "Python机器学习"
keyWord2 = urllib.request.quote(keyWord)
headers = ("User-Agent","MMozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.104 Safari/537.36 Core/1.53.1708.400 QQBrowser/9.5.9635.400")
opener = urllib.request.build_opener()
opener.addheaders = [headers]
urllib.request.install_opener(opener)
url = "https://s.taobao.com/search?q=" + keyWord2 + "&imgfile=&commend=all&ssid=s5-e&search_type=item&sourceId=tb.index&spm=a21bo.50862.201856-taobao-item.1&ie=utf8&initiative_id=tbindexz_20161214"
data = urllib.request.urlopen(url).read().decode("utf-8","ignore")
pat = 'pic_url":"//(.*?)"'#注意，该数据不在Html代码之中，在全局脚本g_page_config
imageList = re.compile(pat).findall(data)
for j in range(0,len(imageList)):
    try:
        curImage = imageList[j]
        curImageUrl = "http://" + curImage
        file="F:/20_Python/3000_Data/" +  str(j) + ".jpg"
        print(file)
        urllib.request.urlretrieve(curImageUrl,filename=file)
    except urllib.error.URLError as e:
        if hasattr(e,"code"):
            print(e.code)
        if hasattr(e,"reason"):
            print(e.reason)
    except Exception as e:
        print(e)

6、正则表达式

 常用正则表达式爬取网页信息及分析HTML标签总结 http://blog.csdn.net/eastmount/article/details/51082253

 如对Python机器学习的正则分析：

pat = 'pic_url":"//(.*?)"'

re.compile(pat).findall(data)

提取（.*?）,位于pic_url":"//和"之中

如对糗事百科的正则分析：

pat='<div class="content">.*?<span>(.*?)</span>.*?</div>'
datalist=re.compile(pat,re.S).findall(pagedata)

7、IP代理

 需要靠谱稳定的IP地址，找到合适的代理替换 proxy_addr

import urllib.request
import random
def use_proxy(url,proxy_addr):
    proxy=urllib.request.ProxyHandler({"http":random.choice(proxy_addr)})
    headers = ("User-Agent","Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/49.0.2623.22 Safari/537.36 SE 2.X MetaSr 1.0")
    opener=urllib.request.build_opener(proxy,urllib.request.HTTPHandler)
    opener.addheaders = [headers]
    urllib.request.install_opener(opener)
    data=urllib.request.urlopen(url).read().decode("utf-8","ignore")
    return data
proxy_addr=["45.64.166.142:8080","80.1.116.80:80","196.15.141.27:8080","47.88.6.158:8118","125.209.97.190  :8080"]
url="http://cuiqingcai.com/1319.html" #http://proxy.com.ru
data=use_proxy(url,proxy_addr)
print(len(data))

8、抓包分析

9、多线程爬取

import threading

class DownPage(threading.Thread):
    def __init__(self):
        threading.Thread.__init__(self)
    def run(self):
        print("处理下载业务业务")

downTask = DownPage()
downTask.start()

10、异常处理

 见：urllib保存图片，使用try：except：捕获异常

11、XPath

 http://www.cnblogs.com/defineconst/p/6181333.html

二、Scrapy安装关联包

 PyCharm---》File---》Settings---》Project..........