Python 爬虫 CSDN 网页下载

import re
import urllib.request
import urllib.error
url="http://blog.csdn.net"
header=("User-Agent",'User-Agent:Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.87 Safari/537.36')
opn=urllib.request.build_opener()
opn.addheaders=[header]
data=opn.open(url).read().decode()
pat='<li class=""><a href="(.*?)">'
menu_data=re.compile(pat).findall(data)
file_num=0
for all_link in menu_data:
    data1=opn.open('http://blog.csdn.net/'+all_link ).read().decode()
    pat1='<a href="(http://blog.csdn.net/.*[0-9].*?)" target=.*'
    sub_menu=re.compile(pat1).findall(data1)
    try:
        for link in sub_menu:
            file_num+=1
            urllib.request.urlretrieve(link,"D:\\data\\"+str(file_num)+".html")
    except urllib.error.URLError  as err:
        if hasattr(err,"code"):
            print(err.code)
        if hasattr(err,"reason"):
            print(err.reason)