网络爬虫-1:发送请求+维持会话+代理设置/超时设置

1.基于get发送请求
2.基于post发送请求
3.维持会话
4.代理设置/超时设置

一.基于get发送请求

1.获取网页源码1

使用json库中的json.loads(),将json格式的字符串变为Python的字典形式

以下通过http://httpbin.org/get网址进行基本练习操作

import requests
import json
url='http://httpbin.org/get'  #目标站点url
r=requests.get(url)           #发送get请求
dict_data=json.loads(r.text)
print("网页源码:\n",r.text)
print("网页源码的类型:\n",type(r.text))
print("键值对形式:\n",dict_data)
print("响应状态码:\n",r.status_code)     

1.网页源码通常为 HTML、JSON 或其他文本格式。

2.通过type函数可知,返回的网页源码是JSON 格式的字符串。

3.响应状态码一般有:200(请求成功),404(未找到),500(服务器内部错误)。

通过以上操作就获得了一个简单的网页源码爬取

网页源码:{"args": {}, "headers": {"Accept": "*/*", "Accept-Encoding": "gzip, deflate", "Host": "httpbin.org", "User-Agent": "python-requests/2.32.3", "X-Amzn-Trace-Id": "Root=1-67b6f01c-2e488d805a9188994c10307a"}, "origin": "112.240.55.236", "url": "http://httpbin.org/get"
}网页源码的类型:<class 'str'>
键值对形式:{'args': {}, 'headers': {'Accept': '*/*', 'Accept-Encoding': 'gzip, deflate', 'Host': 'httpbin.org', 'User-Agent': 'python-requests/2.32.3', 'X-Amzn-Trace-Id': 'Root=1-67b6f01c-2e488d805a9188994c10307a'}, 'origin': '112.240.55.236', 'url': 'http://httpbin.org/get'}
响应状态码:200

2.获取网页源码2

使用r.json()

import requests
import json
url='http://httpbin.org/get'  #目标站点url
r=requests.get(url)           #发送get请求
dict_data=r.json()
print("键值对形式:\n",dict_data)

键值对形式:{'args': {}, 'headers': {'Accept': '*/*', 'Accept-Encoding': 'gzip, deflate', 'Host': 'httpbin.org', 'User-Agent': 'python-requests/2.32.3', 'X-Amzn-Trace-Id': 'Root=1-67b6f1fb-77329c48412b3c3c3c0aa26e'}, 'origin': '112.240.55.236', 'url': 'http://httpbin.org/get'}

3.网页源码(为图片或音频时)

使用r.content

import requestsurl='https://www.baidu.com/img/baidu_jgylogo3.gif'  #以图片为例
r = requests.get(url)                               #发送get请求
print(r.content)                                    #获取为二进制形式,图片或音频
print(type(r.content))                              #<class 'bytes'>表示二进制
#保存二进制图片
with open('test.jpg','wb') as f:f.write(r.content)

4.设置参数1

该练习网站可以自己设置参数args,通过在网址后面加?,参数后面加&,会在args这一栏显示设置的参数

import requests
url='http://httpbin.org/get?age=12&time=11.9&name=12'#目标站点
r=requests.get(url)
print(r.text)

 在返回的网页源码中,会出现我们在url后面设置的参数

{"args": {"age": "12", "name": "12", "time": "11.9"}, "headers": {"Accept": "*/*", "Accept-Encoding": "gzip, deflate", "Host": "httpbin.org", "User-Agent": "python-requests/2.32.3", "X-Amzn-Trace-Id": "Root=1-67b6e74e-2ecdb89860e0144f3c399d39"}, "origin": "112.240.55.236", "url": "http://httpbin.org/get?age=12&time=11.9&name=12"
}

5.设置参数2

推荐使用的参数添加方式:使用字典,并在params参数中加上data,即可实现在网址后加上参数的操作

url='http://httpbin.org/get?'
data={'age':12,'time':11.9
}
r=requests.get(url,params=data)
print(r.text)

{"args": {"age": "12", "time": "11.9"}, "headers": {"Accept": "*/*", "Accept-Encoding": "gzip, deflate", "Host": "httpbin.org", "User-Agent": "python-requests/2.32.3", "X-Amzn-Trace-Id": "Root=1-67a08088-56abf4e11348b1622190c6ca"}, "origin": "123.13.93.50", "url": "http://httpbin.org/get?age=12&time=11.9"
}

6.爬虫伪装-1

import requests
import random
url='https://www.zhihu.com/explore'
#构建用户信息
USER_AGENTS = [
"Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; AcooBrowser; .NET CLR 1.1.4322; .NET CLR 2.0.50727)",
"Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0; Acoo Browser; SLCC1; .NET CLR 2.0.50727; Media Center PC 5.0; .NET CLR 3.0.04506)",
"Mozilla/4.0 (compatible; MSIE 7.0; AOL 9.5; AOLBuild 4337.35; Windows NT 5.1; .NET CLR 1.1.4322; .NET CLR 2.0.50727)",
"Mozilla/5.0 (Windows; U; MSIE 9.0; Windows NT 9.0; en-US)",
"Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Win64; x64; Trident/5.0; .NET CLR 3.5.30729; .NET CLR 3.0.30729; .NET CLR 2.0.50727; Media Center PC 6.0)",
"Mozilla/5.0 (compatible; MSIE 8.0; Windows NT 6.0; Trident/4.0; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; .NET CLR 1.0.3705; .NET CLR 1.1.4322)",
"Mozilla/4.0 (compatible; MSIE 7.0b; Windows NT 5.2; .NET CLR 1.1.4322; .NET CLR 2.0.50727; InfoPath.2; .NET CLR 3.0.04506.30)",
"Mozilla/5.0 (Windows; U; Windows NT 5.1; zh-CN) AppleWebKit/523.15 (KHTML, like Gecko, Safari/419.3) Arora/0.3 (Change: 287 c9dfb30)",
"Mozilla/5.0 (X11; U; Linux; en-US) AppleWebKit/527+ (KHTML, like Gecko, Safari/419.3) Arora/0.6",
"Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.2pre) Gecko/20070215 K-Ninja/2.1.1",
"Mozilla/5.0 (Windows; U; Windows NT 5.1; zh-CN; rv:1.9) Gecko/20080705 Firefox/3.0 Kapiko/3.0",
"Mozilla/5.0 (X11; Linux i686; U;) Gecko/20070322 Kazehakase/0.4.5",
"Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.0.8) Gecko Fedora/1.9.0.8-1.fc10 Kazehakase/0.5.6",
"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.11 (KHTML, like Gecko) Chrome/17.0.963.56 Safari/535.11",
"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_3) AppleWebKit/535.20 (KHTML, like Gecko) Chrome/19.0.1036.7 Safari/535.20",
"Opera/9.80 (Macintosh; Intel Mac OS X 10.6.8; U; fr) Presto/2.9.168 Version/11.52",
"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.11 (KHTML, like Gecko) Chrome/20.0.1132.11 TaoBrowser/2.0 Safari/536.11",
"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.71 Safari/537.1 LBBROWSER",
"Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C; .NET4.0E; LBBROWSER)",
"Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; QQDownload 732; .NET4.0C; .NET4.0E; LBBROWSER)",
"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.11 (KHTML, like Gecko) Chrome/17.0.963.84 Safari/535.11 LBBROWSER",
"Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; WOW64; Trident/5.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C; .NET4.0E)",
"Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C; .NET4.0E; QQBrowser/7.0.3698.400)",
"Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; QQDownload 732; .NET4.0C; .NET4.0E)",
"Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; Trident/4.0; SV1; QQDownload 732; .NET4.0C; .NET4.0E; 360SE)",
"Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; QQDownload 732; .NET4.0C; .NET4.0E)",
"Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; WOW64; Trident/5.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C; .NET4.0E)",
"Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.89 Safari/537.1",
"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.89 Safari/537.1",
"Mozilla/5.0 (iPad; U; CPU OS 4_2_1 like Mac OS X; zh-cn) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8C148 Safari/6533.18.5",
"Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:2.0b13pre) Gecko/20110307 Firefox/4.0b13pre",
"Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:16.0) Gecko/20100101 Firefox/16.0",
"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.64 Safari/537.11",
"Mozilla/5.0 (X11; U; Linux x86_64; zh-CN; rv:1.9.2.10) Gecko/20100922 Ubuntu/10.10 (maverick) Firefox/3.6.10"
]
UA={'User-Agent': random.choice(USER_AGENTS),
}
#参数设置
data={"age":12,"time":11.9
}
response=requests.get(url,params=data,headers=UA)
print("响应状态码:\n",response.status_code)
print("网页源码前200:\n",response.text[:200])

二.基于post发送请求

1.获取网页源码1

使用json库中的json.loads(),将json格式的字符串变为Python的字典形式

import requests
import json
url='http://httpbin.org/post'    #目标站点
r = requests.post(url)           #发送post请求
dict_data=json.loads(r.text)     #将JSON 格式的字符串转换为 Python 字典(方便后续通过键名操作)
url_=dict_data["url"]            #获取网页源码中的url
print("输出json形式的网页源码:\n",dict_data)
print(url_)

输出json形式的网页源码:{'args': {}, 'data': '', 'files': {}, 'form': {}, 'headers': {'Accept': '*/*', 'Accept-Encoding': 'gzip, deflate', 'Content-Length': '0', 'Host': 'httpbin.org', 'User-Agent': 'python-requests/2.32.3', 'X-Amzn-Trace-Id': 'Root=1-67b6ea62-559651c6763bbd4a2659f360'}, 'json': None, 'origin': '112.240.55.236', 'url': 'http://httpbin.org/post'}
http://httpbin.org/post

2.获取网页源码2

使用r.json()

import requests
import json
url='http://httpbin.org/post'#目标站点
r = requests.post(url)
dict_data=r.json()
print(dict_data)
print(dict_data["url"])

{'args': {}, 'data': '', 'files': {}, 'form': {}, 'headers': {'Accept': '*/*', 'Accept-Encoding': 'gzip, deflate', 'Content-Length': '0', 'Host': 'httpbin.org', 'User-Agent': 'python-requests/2.32.3', 'X-Amzn-Trace-Id': 'Root=1-67b6ee93-0580883d7de493eb16e3b93a'}, 'json': None, 'origin': '112.240.55.236', 'url': 'http://httpbin.org/post'}
http://httpbin.org/post

3.设置参数

json形式,基于post请求增加参数,使用data=data进行参数的增加

import requestsurl='http://httpbin.org/post'  #目标站点post请求
data={"age":12,"time":11.9
}                              #参数
response = requests.post(url,data=data)
print("网页源码:\n",response.text)
print("网页源码(键值对形式):\n",response.json())

网页源码:{"args": {}, "data": "", "files": {}, "form": {"age": "12", "time": "11.9"}, "headers": {"Accept": "*/*", "Accept-Encoding": "gzip, deflate", "Content-Length": "16", "Content-Type": "application/x-www-form-urlencoded", "Host": "httpbin.org", "User-Agent": "python-requests/2.32.3", "X-Amzn-Trace-Id": "Root=1-67b6f31c-37e0c7ac11daa02a0d09daad"}, "json": null, "origin": "112.240.55.236", "url": "http://httpbin.org/post"
}网页源码(键值对形式):{'args': {}, 'data': '', 'files': {}, 'form': {'age': '12', 'time': '11.9'}, 'headers': {'Accept': '*/*', 'Accept-Encoding': 'gzip, deflate', 'Content-Length': '16', 'Content-Type': 'application/x-www-form-urlencoded', 'Host': 'httpbin.org', 'User-Agent': 'python-requests/2.32.3', 'X-Amzn-Trace-Id': 'Root=1-67b6f31c-37e0c7ac11daa02a0d09daad'}, 'json': None, 'origin': '112.240.55.236', 'url': 'http://httpbin.org/post'}

三.维持会话

用途:登录网站使用 Cookies 或 Session 维持登录状态，访问需要登录的页面。

3.1通过cookies维持会话

import requests
#好处:容易请求到需要登录的请求
#坏处:容易被反爬封号
head={"cookie":"...............","user-agent":"................"
}
url='https://www.jianshu.com'
response=requests.get(url,headers=head)

3.2通过session维持会话

import requestss=requests.Session()
url='https://www.jianshu.com'
response1 = s.get(url,headers=head)

Cookies 和 Session 的区别

特性	Cookies	Session
存储位置	客户端（浏览器或爬虫）	服务器端
数据安全性	较低（可以被客户端修改）	较高（存储在服务器）
生命周期	可以设置过期时间	通常随会话结束而失效
性能影响	每次请求都会携带 Cookies，增加带宽	服务器需要存储 Session 数据
适用场景	简单的状态维持（如登录状态）	复杂的状态管理（如购物车、多步操作）

四.代理设置/超时设置

使用proxies携带ip地址,使用timeout进行超时反馈,当ip不能用时,防止一直访问而不自知

超时（Timeout）是指爬虫在发送请求后，等待服务器响应的最长时间。如果超过这个时间仍未收到响应，爬虫会停止等待并抛出异常。

url='https://www.jianshu.com'
ip = {"https":"172.16.17.32:8000",
}
response2=requests.get(url,proxies=ip,timeout=4)

 超时参数详解

• timeout=5：表示总超时时间为 5 秒（包括连接时间和读取时间）。

• timeout=(3, 5)：表示连接超时为 3 秒，读取超时为 5 秒。