Python爬虫利器一之Requests库的用法

来源：互联网发布：wiley数据库使用方法编辑：程序博客网时间：2024/05/01 21:29

前言

之前我们用了 urllib 库，这个作为入门的工具还是不错的，对了解一些爬虫的基本理念，掌握爬虫爬取的流程有所帮助。入门之后，我们就需要学习一些更加高级的内容和工具来方便我们的爬取。那么这一节来简单介绍一下 requests 库的基本用法

安装

利用 pip 安装

pip3 install requests

或者利用 easy_install

easy_install requests

通过以上两种方法均可以完成安装。

引入

首先我们引入一个小例子来感受一下

#!/usr/bin/env python3#coding:utf-8import requestsrequest = requests.get('http://www.baidu.com')print('type(request)', type(request))print('request.status_code', request.status_code)print('request.encoding', request.encoding)print('request.cookies', request.cookies)print('request.text', request.text)

以上代码我们请求了本站点的网址，然后打印出了返回结果的类型，状态码，编码方式，Cookies等内容。

运行结果如下

type(request) <class 'requests.models.Response'>request.status_code 200request.encoding ISO-8859-1request.cookies <RequestsCookieJar[<Cookie BDORZ=27315 for .baidu.com/>]>request.text <!DOCTYPE html><!--STATUS OK--><html> <head><meta http-equiv=content-type content=text/html;charset=utf-8><meta http-equiv=X-UA-Compatible content=IE=Edge><meta content=always name=referrer><link rel=stylesheet type=text/css href=http://s1.bdstatic.com/r/www/cache/bdorz/baidu.min.css><title>ç™¾åº¦ä¸€ä¸‹ï¼Œä½ å°±çŸ¥é“</title></head> <body link=#0000cc> <div id=wrapper> <div id=head> <div class=head_wrapper> <div class=s_form> <div class=s_form_wrapper> <div id=lg> <img hidefocus=true src=//www.baidu.com/img/bd_logo1.png width=270 height=129> </div> <form id=form name=f action=//www.baidu.com/s class=fm> <input type=hidden name=bdorz_come value=1> <input type=hidden name=ie value=utf-8> <input type=hidden name=f value=8> <input type=hidden name=rsv_bp value=1> <input type=hidden name=rsv_idx value=1> <input type=hidden name=tn value=baidu><span class="bg s_ipt_wr"><input id=kw name=wd class=s_ipt value maxlength=255 autocomplete=off autofocus></span><span class="bg s_btn_wr"><input type=submit id=su value=ç™¾åº¦ä¸€ä¸‹ class="bg s_btn"></span> </form> </div> </div> <div id=u1> <a href=http://news.baidu.com name=tj_trnews class=mnav>æ–°é—»</a> <a href=http://www.hao123.com name=tj_trhao123 class=mnav>hao123</a> <a href=http://map.baidu.com name=tj_trmap class=mnav>åœ°å›¾</a> <a href=http://v.baidu.com name=tj_trvideo class=mnav>è§†é¢‘</a> <a href=http://tieba.baidu.com name=tj_trtieba class=mnav>è´´å§</a> <noscript> <a href=http://www.baidu.com/bdorz/login.gif?login&amp;tpl=mn&amp;u=http%3A%2F%2Fwww.baidu.com%2f%3fbdorz_come%3d1 name=tj_login class=lb>ç™»å½•</a> </noscript> <script>document.write('<a href="http://www.baidu.com/bdorz/login.gif?login&tpl=mn&u='+ encodeURIComponent(window.location.href+ (window.location.search === "" ? "?" : "&")+ "bdorz_come=1")+ '" name="tj_login" class="lb">ç™»å½•</a>');</script> <a href=//www.baidu.com/more/ name=tj_briicon class=bri style="display: block;">æ›´å¤šäº§å“</a> </div> </div> </div> <div id=ftCon> <div id=ftConw> <p id=lh> <a href=http://home.baidu.com>å…³äºŽç™¾åº¦</a> <a href=http://ir.baidu.com>About Baidu</a> </p> <p id=cp>&copy;2017&nbsp;Baidu&nbsp;<a href=http://www.baidu.com/duty/>ä½¿ç”¨ç™¾åº¦å‰å¿…è¯»</a>&nbsp; <a href=http://jianyi.baidu.com/ class=cp-feedback>æ„è§åé¦ˆ</a>&nbsp;äº¬ICPè¯030173å·&nbsp; <img src=//www.baidu.com/img/gs.gif> </p> </div> </div> </div> </body> </html>

基本请求

requests库提供了http所有的基本请求方式。例如

request = requests.get(url)request = requests.post(url)request = requests.put(url)request = requests.delete(url)request = requests.head(url)request = requests.opinions(url)

GET请求

基本GET请求

最基本的GET请求可以直接用get方法

#!/usr/bin/env python3#coding:utf-8import requestsparams = {    'key1': 'value1',    'key2': 'value2'}request = requests.get('http://httpbin.org/get', params=params)print(request.url)

运行结果

http://httpbin.org/get?key1=value1&key2=value2

GET JSON

我们能读取服务器响应的内容。以 GitHub 时间线为例：

#!/usr/bin/env python3#coding:utf-8import requestsrequest = requests.get('https://api.github.com/events')print('request.text', request.text)print('request.json()', request.json)

输出

request.text [{"id":"5435287313","type":"PushEvent","actor":=...}]request.json() <bound method Response.json of <Response [200]>>

GET原始套接字内容

如果想获取来自服务器的原始套接字响应，可以取得 r.raw 。不过需要在初始请求中设置 stream=True

#!/usr/bin/env python3#coding:utf-8import requestsrequest = requests.get('https://api.github.com/events', stream=True)print('request.raw', request.raw)print('request.raw.read(10)', request.raw.read(10))

这样就获取了网页原始套接字内容

request.raw <requests.packages.urllib3.response.HTTPResponse object at 0x106b5f9b0>request.raw.read(10) b'\x1f\x8b\x08\x00\x00\x00\x00\x00\x00\x03'

添加headers

通过传递headers参数来添加headers

#!/usr/bin/env python3#coding:utf-8import requestsparams = {    'key1': 'value1',    'key2': 'value2'}headers= {    'content-type': 'application/json'}request = requests.get('http://httpbin.org/get', params=params, headers=headers)print(request.url)

输出

http://httpbin.org/get?key1=value1&key2=value2

POST请求

基本POST请求

对于 POST 请求来说，我们一般需要为它增加一些参数。那么最基本的传参方法可以利用data 这个参数

#!/usr/bin/env python3#coding:utf-8import requestsdata = {    'key1': 'value1',    'key2': 'value2'}request = requests.post('http://httpbin.org/post', data=data)print('request.text', request.text)

输出结果

request.text {  "args": {},  "data": "",  "files": {},  "form": {    "key1": "value1",    "key2": "value2"  },  "headers": {    "Accept": "*/*",    "Accept-Encoding": "gzip, deflate",    "Content-Length": "23",    "Content-Type": "application/x-www-form-urlencoded",    "Host": "httpbin.org",    "User-Agent": "python-requests/2.13.0"  },  "json": null,  "origin": "120.236.174.172",  "url": "http://httpbin.org/post"}

POST JSON

有时候我们需要传送的信息不是表单形式的，需要我们传JSON格式的数据过去，所以我们可以用json.dumps()方法把表单数据序列化

#!/usr/bin/env python3#coding:utf-8import jsonimport requestsdata = {    'some': 'data'}request = requests.post('http://httpbin.org/post', data=json.dumps(data))print('request.text', request.text)

输出

request.text {  "args": {},  "data": "{\"some\": \"data\"}",  "files": {},  "form": {},  "headers": {    "Accept": "*/*",    "Accept-Encoding": "gzip, deflate",    "Content-Length": "16",    "Host": "httpbin.org",    "User-Agent": "python-requests/2.13.0"  },  "json": {    "some": "data"  },  "origin": "120.236.174.172",  "url": "http://httpbin.org/post"}

在2.4.2版本后，直接使用json参数就可以进行编码

#!/usr/bin/env python3#coding:utf-8import jsonimport requestsdata = {    'some': 'data'}# request = requests.post('http://httpbin.org/post', data=json.dumps(data))request = requests.post('http://httpbin.org/post', json=data)print('request.text', request.text)

上传文件

如果想要上传文件，那么直接用files参数即可

#!/usr/bin/env python3#coding:utf-8import requestsfiles = {    'file': open('test.txt', 'rb')}request = requests.post('http://httpbin.org/post', files=files)print('request.text', request.text)

输出

request.text {  "args": {},  "data": "",  "files": {    "file": "hello word!\n"  },  "form": {},  "headers": {    "Accept": "*/*",    "Accept-Encoding": "gzip, deflate",    "Content-Length": "156",    "Content-Type": "multipart/form-data; boundary=e76e934f387f4013a0cb03f0cc7f636d",    "Host": "httpbin.org",    "User-Agent": "python-requests/2.13.0"  },  "json": null,  "origin": "120.236.174.172",  "url": "http://httpbin.org/post"}

上传流

requests 是支持流式上传的，这允许你发送大的数据流或文件而无需先把它们读入内存。要使用流式上传，仅需为你的请求体提供一个类文件对象即可

#!/usr/bin/env python3#coding:utf-8import requestswith open('test.txt', 'rb') as f:    request = requests.post('http://httpbin.org/post', data=f)print('request.text', request.text)

输出结果和直接用文件上传一样

Cookies

如果一个响应中包含了cookie，那么我们可以利用 cookies 变量来拿到

也可以利用cookies参数来向服务器发送cookies信息

#!/usr/bin/env python3#coding:utf-8import requestsrequest = requests.get('http://httpbin.org/cookies')print('request.cookies', requests.cookies)print('request.text', request.text)cookies = {    'cookies_are': 'working'}request = requests.get('http://httpbin.org/cookies', cookies=cookies)print('request.cookies', requests.cookies)print('request.text', request.text)

输出

request.cookies <module 'requests.cookies' from '/usr/local/lib/python3.6/site-packages/requests/cookies.py'>request.text {  "cookies": {}}request.cookies <module 'requests.cookies' from '/usr/local/lib/python3.6/site-packages/requests/cookies.py'>request.text {  "cookies": {    "cookies_are": "working"  }}

超时配置

可以利用 timeout 变量来配置最大请求时间

#!/usr/bin/env python3#coding:utf-8import requestsrequest = requests.get('http://www.google.com.hk', timeout=0.01)print(request.url)

如果超时，会抛出一个异常

Traceback (most recent call last):  File "/usr/local/lib/python3.6/site-packages/requests/packages/urllib3/connection.py", line 141, in _new_conn    (self.host, self.port), self.timeout, **extra_kw)  File "/usr/local/lib/python3.6/site-packages/requests/packages/urllib3/util/connection.py", line 83, in create_connection    raise err  File "/usr/local/lib/python3.6/site-packages/requests/packages/urllib3/util/connection.py", line 73, in create_connection    sock.connect(sa)socket.timeout: timed out

会话对象

在以上的请求中，每次请求其实都相当于发起了一个新的请求。也就是相当于我们每个请求都用了不同的浏览器单独打开的效果。也就是它并不是指的一个会话，即使请求的是同一个网址。比如

#!/usr/bin/env python3#coding:utf-8import requestsrequests.get('http://httpbin.org/cookies/set/sessioncookie/123456789')request = requests.get('http://httpbin.org/cookies')print(request.text)

输出

{  "cookies": {}}

很明显，这不在一个会话中，无法获取 cookies，那么在一些站点中，我们需要保持一个持久的会话怎么办呢？就像用一个浏览器逛淘宝一样，在不同的选项卡之间跳转，这样其实就是通过request.Session建立了一个长久会话

解决方案如下

#!/usr/bin/env python3#coding:utf-8import requests# 通过session建立长久会话session = requests.Session()session.get('http://httpbin.org/cookies/set/sessioncookie/123456789')request = session.get('http://httpbin.org/cookies')print(request.text)

输出

{  "cookies": {    "sessioncookie": "123456789"  }}

发现可以成功获取到 cookies 了，这就是建立一个会话到作用。体会一下。

那么既然会话是一个全局的变量，那么我们肯定可以用来全局的配置了。

当在会话中设置headers，又在请求中设置headers，两个变量都会传送过去

#!/usr/bin/env python3#coding:utf-8import requestsheaders1 = {    'test1': 'true'}headers2 = {    'test2': 'true'}session = requests.Session()session.headers.update(headers1)request = session.get('http://httpbin.org/headers', headers=headers2)print(request.text)

输出

{  "headers": {    "Accept": "*/*",    "Accept-Encoding": "gzip, deflate",    "Host": "httpbin.org",    "Test1": "true",    "Test2": "true",    "User-Agent": "python-requests/2.13.0"  }}

SSL证书验证

现在随处可见 https 开头的网站，Requests可以为HTTPS请求验证SSL证书，就像web浏览器一样。要想检查某个主机的SSL证书，你可以使用 verify参数（默认为True）

现在 12306 证书不是无效的嘛，来测试一下

#!/usr/bin/env python3#coding:utf-8import requestsrequest = requests.get('https://kyfw.12306.cn/otn', verify=True)print(request.text)

输出

Traceback (most recent call last):  File "/usr/local/lib/python3.6/site-packages/requests/packages/urllib3/contrib/pyopenssl.py", line 436, in wrap_socket    cnx.do_handshake()  File "/usr/local/lib/python3.6/site-packages/OpenSSL/SSL.py", line 1426, in do_handshake    self._raise_ssl_error(self._ssl, result)  File "/usr/local/lib/python3.6/site-packages/OpenSSL/SSL.py", line 1174, in _raise_ssl_error    _raise_current_error()  File "/usr/local/lib/python3.6/site-packages/OpenSSL/_util.py", line 48, in exception_from_error_queue    raise exception_type(errors)OpenSSL.SSL.Error: [('SSL routines', 'ssl3_get_server_certificate', 'certificate verify failed')]

如果想跳过证书验证，只需要把verify设置为False

来试下 github 的

#!/usr/bin/env python3#coding:utf-8import requestsrequest = requests.get('https://kyfw.12306.cn/otn', verify=True)print(request.text)

请求正常

代理

如果需要使用代理，你可以通过为任意请求方法提供 proxies 参数来配置单个请求

#!/usr/bin/env python3#coding:utf-8import requestsproxies = {    "https://www.google.com.hk/": "192.168.199.101"}request = requests.get('https://www.google.com.hk/', proxies=proxies)print(request.text)

API

以上讲解了 requests 中最常用的参数，如果需要用到更多，请参考官方文档 API

API

结语

以上总结了一下 requests 的基本用法，如果你对爬虫有了一定的基础，那么肯定可以很快上手，在此就不多赘述了。

练习才是王道，大家尽快投注于实践中吧

转载于：静觅 » Python爬虫利器一之Requests库的用法

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