python爬虫之requests库的使用详解_Python

python爬虫―requests库的用法

requests是python实现的简单易用的HTTP库，使用起来比urllib简洁很多，requests 允许你发送 HTTP/1.1 请求。指定 URL并添加查询url字符串即可开始爬取网页信息等操作

因为是第三方库，所以使用前需要cmd安装

pip install requests

安装完成后import一下，正常则说明可以开始使用了

基本用法：

requests.get()用于请求目标网站，类型是一个HTTPresponse类型

import requests
response = requests.get('http://www.baidu.com')
print(response.status_code)  # 打印状态码
print(response.url)          # 打印请求url
print(response.headers)      # 打印头信息
print(response.cookies)      # 打印cookie信息
print(response.text)  #以文本形式打印网页源码
print(response.content) #以字节流形式打印

以打印状态码为例，运行结果：

python爬虫之requests库的使用详解

状态码：200，证明请求目标网站正常

若状态码为403一般是目标存有防火墙，触发了反爬策略被限制了IP

各种请求方式：

import requests
requests.get('http://www.baidu.com')
requests.post('http://www.baidu.com')
requests.put('http://www.baidu.com')
requests.delete('http://www.baidu.com')
requests.head('http://www.baidu.com')
requests.options('http://www.baidu.com')

基本的get请求

import requests
response = requests.get('http://www.baidu.com')
print(response.text)

python爬虫之requests库的使用详解

带参数的GET请求：

第一种直接将参数放在url内

import requests
response = requests.get("https://www.crrcgo.cc/admin/crr_supplier.html?params=1")
print(response.text)

python爬虫之requests库的使用详解

另一种先将参数填写在data中，发起请求时将params参数指定为data

import requests
data = {
  'params': '1',
}
response = requests.get('https://www.crrcgo.cc/admin/crr_supplier.html?', params=data)
print(response.text)

python爬虫之requests库的使用详解

基本POST请求：

import requests
response = requests.post('http://baidu.com')

python爬虫之requests库的使用详解

解析json

import requests
response = requests.get('http://httpbin.org/get')
print(response.text)
print(response.json())  #response.json()方法同json.loads(response.text)
print(type(response.json()))

python爬虫之requests库的使用详解

简单保存一个二进制文件

import requests
response = requests.get('http://img.ivsky.com/img/tupian/pre/201708/30/kekeersitao-002.jpg')
b = response.content
with open('F://fengjing.jpg','wb') as f:
  f.write(b)

为你的请求添加头信息

import requests
heads = {}
heads['User-Agent'] = 'Mozilla/5.0 ' \
                        '(Macintosh; U; Intel Mac OS X 10_6_8; en-us) AppleWebKit/534.50 ' \
                        '(KHTML, like Gecko) Version/5.1 Safari/534.50'
response = requests.get('http://www.baidu.com',headers=headers)

此方法可以有效地避开防火墙的检测，隐藏自己身份

使用代理

同添加headers方法一样，代理参数也是一个dict这里使用requests库爬取了IP代理网站的IP与端口和类型。因为是免费的，使用的代理地址很快就失效了。

复制代码

import requests
import re
def get_html(url):
  proxy = {
      'http': '120.25.253.234:812',
      'https' '163.125.222.244:8123'
  }
  heads = {}
  heads['User-Agent'] = 'Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/49.0.2623.221 Safari/537.36 SE 2.X MetaSr 1.0'
  req = requests.get(url, headers=heads,proxies=proxy)
  html = req.text
  return html
def get_ipport(html):
  regex = r'<td data-title="IP">(.+)</td>'
  iplist = re.findall(regex, html)
  regex2 = '<td data-title="PORT">(.+)</td>'
  portlist = re.findall(regex2, html)
  regex3 = r'<td data-title="类型">(.+)</td>'
  typelist = re.findall(regex3, html)
  sumray = []
  for i in iplist:
      for p in portlist:
          for t in typelist:
              pass
          pass
      a = t+','+i + ':' + p
      sumray.append(a)
  print('高匿代理')
  print(sumray)
if __name__ == '__main__':
  url = 'http://www.baidu.com'
  get_ipport(get_html(url))

获取cookie

import requests
response = requests.get('http://www.baidu.com')
print(response.cookies)
print(type(response.cookies))
for k,v in response.cookies.items():
  print(k+':'+v)

python爬虫之requests库的使用详解

会话维持

import requests
session = requests.Session()
session.get('https://www.crrcgo.cc/admin/crr_supplier.html')
response = session.get('https://www.crrcgo.cc/admin/')
print(response.text)

证书验证设置

import requests
from requests.packages import urllib3
urllib3.disable_warnings()  #从urllib3中消除警告
response = requests.get('https://www.12306.cn',verify=False)  #证书验证设为FALSE
print(response.status_code)

超时异常捕获

import requests
from requests.exceptions import ReadTimeout
try:
  res = requests.get('http://httpbin.org', timeout=0.1)
  print(res.status_code)
except ReadTimeout:
  print(timeout)

异常处理

使用try…except来捕获异常

import requests
from requests.exceptions import ReadTimeout,HTTPError,RequestException
try:
  response = requests.get('http://www.baidu.com',timeout=0.5)
  print(response.status_code)
except ReadTimeout:
  print('timeout')
except HTTPError:
  print('httperror')
except RequestException:
  print('reqerror')