python3.6.2下载网页的3种方法

这里运用了python里面的urllib作为网页的下载模块，三种方法的具体的代码如下：

from urllib import request
import http.cookiejar
url="http://www.baidu.com"

print ('第一种方法')
response1=request.urlopen(url)
print (response1.getcode())
print (len(response1.read()))

print ('第二种方法')
req=request.Request(url)
req.add_header('user-agent','Mozilla/5.0')
response2=request.urlopen(req)
print (response2.getcode())
print (len(response2.read()))

print ('第三种方法')
cj=http.cookiejar.CookieJar()
opener=request.build_opener(request.HTTPCookieProcessor(cj))
request.install_opener(opener)
response3=request.urlopen(url)
print (response3.getcode())
print (cj)
print (response3.read())