爬虫2：urllib

 

 

了解即可，不好用

 

一. 概述

 

python内置的http请求库，包括4个模块，分别如下

 

urllib.request   请求模块

urllib.error       异常处理模块

urllib.parse      url解析模块, 工具模块

urllib.robotparser    robots.txt解析模块

 

 

 

urlopen

python2和python3中urlopen方法的不同用法

 

python2中

import urllib2

response=urllib2.urlopen('http://www.baidu.com')

 

python3中

import urllib.request

response=urllib.request.urlopen('http://www.baidu.com')

 

二. urlopen用法

 

1. 获取普通源代码，get方法

import urllib.request

response=urllib.request.urlopen('http://www.baidu.com')
print(response.read().decode('utf-8')

2. post方法请求，传入一个字典

import urllib.parse
import urllib.request

data=bytes(urllib.parse.urlencode({'word':'hello'}), encoding='utf8') //传入一个值
response=urllib.request.urlopen('http://httpbin.org/post', data=data)
print(response.read())

3. 超时操作,在指定时间内未得到响应就抛出异常

import urllib.request

response = urllib.request.urlopen('http://httpbin.org/get', timeout=1)
print(response.read())

 

4. 查看异常

import socket
import urllib.request
import urllib.error

try:
    response = urllib.request.urlopen('http://httpbin.org/get', timeout=0.1)
except urllib.error.URLError as e:
    if isinstance(e.reason, socket.timeout):
        print('TIME OUT')

 

 

三. 响应

 

1. 响应类型

import urllib.request

response = urllib.request.urlopen('https://www.python.org')
print(type(response))

 

2. 状态码，响应头

import urllib.request

response = urllib.request.urlopen('https://www.python.org')
print(response.status)
print(response.getheaders())   //数组的形式，每个数组元素都是一个元组
print(response.getheader('Server'))  //获取数组元素中元组键名为Server的值

 

3. Request()方法单独使用来请求页面

 

import urllib.request

request = urllib.request.Request('https://python.org')
response = urllib.request.urlopen(request)
print(response.read().decode('utf-8'))

---

可以在请求中加入头信息等数据

from urllib import request,parse

url = 'http://httpbin.org/post'
headers = {
    'User-Agent': 'Mozilla/4.0(compatible; MSIE 5.5; Windows NT)',
    'Host': 'httpbin.org'
}
dict = {
    'name': 'Germey'
}
data = bytes(parse.urlencode(dict), encoding='utf8')
req = request.Requests(url=url, data=data, headers=headers, method='POST')
response = request.urlopen(req)
print(response.read().decode('utf-8'))

 

 

---

使用add_header()方法来添加header

 

from urllib import request, parse

url = 'http://httpdbin.org/post'
dict = {
    'name': 'Germey'
}
data = bytes(parse.urlencode(dict), encoding='utf8')
req = request.Requests(url=url, data=data,  method='POST')
req.add_header('User-Agent', 'Mozilla/4.0(compatible; MSIE 5.5; Windows NT)')
response = request.urlopen(req)
print(response.read().decode('utf-8'))

 

 

 

4. Handler

 

1. 代理

 

import urllib.request

proxy_handler = urllib.request.ProxyHander({
    'http':'http://127.0.0.1:9743'
    'https':'https://127.0.0.1:9743'
})
opener = urllib.requets.build_opener(proxy_handler)
response =  opener.open('http://www.baidu.com')
print(response.read())

 

 

2. Cookie

 

例子1，打印出cookie信息

import http.cookiejar,urlib.request

cookie = http.cookiejar.CookieJar()
handler = urllib.request.HTTPCookieProcessor(cookie)
opener = urllib.request.build_opener(handler)
response = opener.open('http://www.baidu.com')
for item in cookie:
    print(item.name+"="+item.value)

 

例子2，保存cookie信息到文本文件

import http.cookiejar, urllib.requst
filename = 'cookie.txt'
cookie = http.cookiejar.MozillaCookieJar(filename)
handler = urllib.request.HTTPCookieProcessor(cookie)
opener = urllib.requst.build_opener(handler)
response = opener.open('http://www.baidu.com')
cookie.save(ignore_discard=True, ignore_expires=True)

 

 

例子3，另外一种保存方法

import http.cookiejar, urllib.request
filename = 'cookie.txt'
cookie = http.cookiejar.LWPCookieJar(filename)
handler = urllib.request.HTTPCookieProcessor(cookie)
opener = urllib.request.build_opener(hander)
response = opener.open('http://www.baidu.com')
cookie.save(ignore_discard=True, ignore_expires=True)

 

 

例子4，读取cookie文件

import http.cookiejar, urllib.request
cookie = http.cookiejar.LWPCookieJar()
cookie.load('cookie.txt', ignore_discard=True, ignore_expires=True)
handler = urllib.request.HTTPCookieProcessor(cookie)
opener = urllib.request.build_opener(handler)
response = opener.open('http://www.baidu.com')
print(response.read().decode('utf-8'))

 

 

5. 异常处理

一般可捕获3个异常类型，分别为URLError, HTTPError, ContentTooShortError

 

1. 打印异常原因, URLError：只有一个reason属性

from urllib import request, error
try:
    response = request.urlopen('http://cuiqingcai.com/index.html')
except error.URLError as e:
    print(e.reason)

 

2. HTTPError是URLError的子类，有三个属性：code，reason，headers

from urllib import request, error

try:
    response = request.urlopen('http://cuiqingcai.com/index.htm')
except error.HTTPError as e:
    print(e.reason, e.code, e.headers, sep='\n')
except error,URLError as e:
    print(e.reason)
else:
    print('Request Successfully')

 

 

3. 验证异常原因

import socket
import urllib.request
import urllib.error

try:
    response = urllib.request.urlopen('https://www.baidu.com',timeout=0.01)
except urllib.error.URLError as e:
    print(type(e.reason))
    if isinstance(e.reason, socket.timeout):
        print('TIME OUT')

 

 

六. URL解析

 

urlparse模块

 

语法：urllib.parse.urlparse(urlstring, scheme='', allow_fragments=True)

 

1. 拆分URL并分段获取URL地址

from urllib.parse import urlparse

result = urlparse('http://www.baidu.com/index.html;user?id=5#comment')
print(type(result), result)

返回结果如下
<class 'urllib.parse.ParseResult'> ParseResult(scheme='http', netloc='www.baidu.com', path='/index.html', params='user', query='id=5', fragment='comment')

 

 

2. 1 URL中不写协议时，scheme参数指定协议类型

from urllib.parse import urlparse

result = urlparse('www.baidu.com/index.html;user?id=5#comment', scheme='https')
print(result)
返回结果如下
ParseResult(scheme='https', netloc='', path='www.baidu.com/index.html', params='user', query='id=5', fragment='comment')

 

 

2. 2 URL中有协议时，scheme参数指定协议类型无效

from urllib.parse import urlparse

result = urlparse('http://www.baidu.com/index.html;user?id=5#comment', scheme='https')
print(result)
返回结果
ParseResult(scheme='http', netloc='www.baidu.com', path='/index.html', params='user', query='id=5', fragment='comment')

 

 

3.1 allow_fragments：锚点链接

from urllib.parse import urlparse

result = urlparse('http://www.baidu.com/index.html;user?id=5#comment', allow_fragments=False)
print(result)
返回结果, 值为False时，锚点值拼接到query中
ParseResult(scheme='http', netloc='www.baidu.com', path='/index.html', params='user', query='id=5#comment', fragment='')

 

 

3.2 当query和params为空时，拼接到前面

from urllib.parse import urlparse

result = urlparse('http://www.baidu.com/index.html#comment', allow_fragments=False)
print(result)
返回结果
ParseResult(scheme='http', netloc='www.baidu.com', path='/index.html#comment', params='', query='', fragment='')

 

 

4. urlunparse模块，拼接url

from urllib.parse import urlunparse

data = ['http', 'www.baidu.com', 'index.html', 'user', 'a=6', 'comment']
print(urlunparse(data))

返回结果：
http://www.baidu.com/index.html;user?a=6#comment

 

 

5. urljoin模块

 

有相同字段的URL，后面的覆盖前面的

from urllib.parse import urljoin

print(urljoin('http://www.baidu.com', 'FAQ.html'))
print(urljoin('http://www.baidu.com', 'https://cuiqingcai.com/FAQ.html'))
print(urljoin('http://www.baidu.com/about.html', 'https://cuiqingcai.com/FAQ.html'))
print(urljoin('http://www.baidu.com/about.html', 'https://cuiqingcai.com/FAQ.html?question=2'))
print(urljoin('http://www.baidu.com?wd=abc', 'https://cuiqingcai.com/index.php'))
print(urljoin('http://www.baidu.com', '?category=2#comment'))
print(urljoin('www.baidu.com', '?category=2#comment'))
print(urljoin('www.baidu.com#comment', '?category=2'))

返回结果为

http://www.baidu.com/FAQ.html

https://cuiqingcai.com/FAQ.html

https://cuiqingcai.com/FAQ.html

https://cuiqingcai.com/FAQ.html?question=2

https://cuiqingcai.com/index.php

http://www.baidu.com?category=2#comment

www.baidu.com?category=2#comment

www.baidu.com?category=2

 

 

 

6. urlencode模块：把字典对象转换为get请求参数

from urllib.parse import urlencode

params = {
    'name': 'germey',
    'age': 22
}
base_url = 'http://www.baidu.com?'
url = base_url + urlencode(params)
print(url)

返回

http://www.baidu.com?name=germey&age=22