• 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='
    ')
    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

     
     
     
    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
     
     
     
     
     
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  • 原文地址:https://www.cnblogs.com/regit/p/9243640.html
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