爬虫笔记：Urllib库详解

素颜马尾好姑娘i 2023-01-09 15:45 154阅读 0赞

如果不懂爬虫，请看链接  
[爬虫第一课：爬虫的基本原理][Link 1]

## 什么是Urllib ##

Urllib是python 内置的http的请求库。包含四个模块

*  urllib.request 请求模块
 *  urllib.error 异常处理模块
 *  urllib.parse url解析模块
 *  urllib.robotparser robots.txt解析模块（识别哪些网站可以爬）  
    本文主要讲解前面三个模块

和python2中urlib模块区别

> Python2  
> import urllib2  
> response = urllib2.urlopen(‘http://www.baidu.com’)

> Python3  
> import urllib.request  
> response = urllib.request.urlopen(‘http://www.baidu.com’)

## 用法讲解 ##

**请求urlopen**  
urlopen

第一个参数URL请求网站，第二个参数data，post请求时需要，第三参数timeout限时设置，后面暂时用不到

#%% raw
    urllib.request.urlopen(url, data=None, [timeout, ]*, cafile=None, capath=None, cadefault=False, context=None)

get请求网页打开

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

![20210122092900694.png_pic_center][]

post请求网页打开

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

![20210122093345924.png_pic_center][]

timeout  
设置一个超时时间，如果在规定时间没有完成请求，会报错

import urllib.request
    
    response = urllib.request.urlopen('http://httpbin.org/get', timeout=0.1)
    print(response.read())

![20210122093835524.png_pic_center][]

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')

**响应**

响应类型

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

![20210122094426664.png_pic_center][]

状态码和响应头  
响应里面，包括两个重要信息：状态码和响应头

import urllib.request
    
    response = urllib.request.urlopen('https://www.python.org')
    print(response.status)#状态码
    print(response.getheaders())#响应头
    print(response.getheader('Server'))#查看响应头具体某一项

![20210122094757766.png_pic_center][]

读取响应read

\#读取的响应为字节流型数据，需要解码为utf-8

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

![20210122095110879.png_pic_center][]

**Request**  
通过前面urlopen 我们可以请求一个网页并获取响应，但urlopen没法添加额外信息，如请求头，所以需要更高级的请求，Request

读取网页

import urllib.request
    
    request = urllib.request.Request('https://python.org')#声明一个request对象
    response = urllib.request.urlopen(request)
    print(response.read().decode('utf-8'))

添加请求头，同时post方式读取网页

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')#编码
    req = request.Request(url=url, data=data, headers=headers, method='POST')
    response = request.urlopen(req)
    print(response.read().decode('utf-8'))

![20210122095950455.png_pic_center][]

前面添加请求头是通过参数，还可以通过add\_header方法

from urllib import request, parse
    
    url = 'http://httpbin.org/post'
    dict = { 
        'name': 'Germey'
    }
    data = bytes(parse.urlencode(dict), encoding='utf8')
    req = request.Request(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'))

**Handler代理**

import urllib.request
    
    proxy_handler = urllib.request.ProxyHandler({ 
        'http': 'http://127.0.0.1:9743',#服务器网址
        'https': 'https://127.0.0.1:9743'
    })
    opener = urllib.request.build_opener(proxy_handler)
    response = opener.open('http://httpbin.org/get')
    print(response.read())

**Cookie**  
Cookie是在客户端保存的，用来记录用户身份的文本文件

如我们打开淘宝网页，左上角显示着用户名信息  
![20210122101753618.png_pic_center][]

审查元素，找到淘宝cookie，右键clear  
![20210122102035159.png_pic_center][]  
![20210122102146223.png_pic_center][]

刷新网页 用户登录信息消失  
![20210122102245174.png_pic_center][]

cookie如果有，可以维持用户登录信息，在做爬虫时，可以爬取一些登录后的信息。  
1.打印cookie

import http.cookiejar, urllib.request
    
    cookie = http.cookiejar.CookieJar()#声明cookie对象
    handler = urllib.request.HTTPCookieProcessor(cookie)
    opener = urllib.request.build_opener(handler)
    response = opener.open('http://www.baidu.com/')#百度，我登录了百度账号
    for item in cookie:
        print(item.name+"="+item.value)

![20210122102638741.png_pic_center][] 2.保存cookie为文本文件

方式1

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

![20210122102910881.png_pic_center][]

方式2

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

![20210122103054191.png_pic_center][]

3.带cookie读取网页

import http.cookiejar, urllib.request
    cookie = http.cookiejar.LWPCookieJar()#要和前面保存方式一样
    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'))

![20210122103325788.png_pic_center][]

**异常处理**

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

![20210122104044113.png_pic_center][]

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')

![20210122104213192.png_pic_center][]

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')

![20210122104322884.png_pic_center][]

**URL解析**  
urlparse  
传入一个url，然后把一个url分割成几个部分。协议，域名，参数等

urllib.parse.urlparse(urlstring, scheme=’’, allow\_fragments=True)

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

![20210122104859900.png_pic_center][]

指定协议类型，传入的ur无协议

from urllib.parse import urlparse
    
    result = urlparse('www.baidu.com/index.html;user?id=5#comment', scheme='https')
    print(result)

指定默认协议为ihttps，如果传入的url无协议就会被指定为https

from urllib.parse import urlparse
    
    result = urlparse('http://www.baidu.com/index.html;user?id=5#comment', scheme='https')
    print(result)

锚点拼接allow\_fragments

from urllib.parse import urlparse
    
    result = urlparse('http://www.baidu.com/index.html;user?id=5#comment', allow_fragments=False)#allow_fragments锚点
    print(result)

urlunparse：拼接URL

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

![20210122105506427.png_pic_center][]

**urljoin**

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'))

![20210122110752915.png_pic_center][]

**urlencode**  
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)

![20210122110956981.png_pic_center][]

![在这里插入图片描述][20210122111353879.jpg_pic_center]  
作者：电气-余登武。  
创作不易，大佬请留步… 来个赞再走呗 (๑◕ܫ￩๑)

[Link 1]: https://blog.csdn.net/KOBEYU652453/article/details/112862664
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