Python如何安装urllib2库

#urllib2_useragent.py
 
import urllib2
 
url = "http://www.itcast.cn"
 
#IE 9.0 的 User-Agent，包含在 ua_header里
ua_header = {"User-Agent" : "Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0;"} 
 
# url 连同 headers，一起构造Request请求，这个请求将附带 IE9.0 浏览器的User-Agent
request = urllib2.Request(url, headers = ua_header)
 
# 向服务器发送这个请求
response = urllib2.urlopen(request)
 
html = response.read()
print html

# urllib2_headers.py
 
import urllib2
 
url = "http://www.itcast.cn"
 
#IE 9.0 的 User-Agent
header = {"User-Agent" : "Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0;"} 
request = urllib2.Request(url, headers = header)
 
#也可以通过调用Request.add_header() 添加/修改一个特定的header
request.add_header("Connection", "keep-alive")
 
# 也可以通过调用Request.get_header()来查看header信息
# request.get_header(header_name="Connection")
 
response = urllib2.urlopen(req)
 
print response.code #可以查看响应状态码
html = response.read()
 
print html

# urllib2_add_headers.py
 
import urllib2
import random
 
url = "http://www.itcast.cn"
 
ua_list = [
 "Mozilla/5.0 (Windows NT 6.1; ) Apple.... ",
 "Mozilla/5.0 (X11; CrOS i686 2268.111.0)... ",
 "Mozilla/5.0 (Macintosh; U; PPC Mac OS X.... ",
 "Mozilla/5.0 (Macintosh; Intel Mac OS... "
]
 
user_agent = random.choice(ua_list)
 
request = urllib2.Request(url)
 
#也可以通过调用Request.add_header() 添加/修改一个特定的header
request.add_header("User-Agent", user_agent)
 
# 第一个字母大写，后面的全部小写
request.get_header("User-agent")
 
response = urllib2.urlopen(req)
 
html = response.read()
print html