python爬虫之requests库的使用详解

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：

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)

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)

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)

基本post请求：

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

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()))

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)

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')

总结

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