02 requests模块

requests模块

    requests是用python语言基于urllib编写的，采用的是Apache2 Licensed开源协议的HTTP库，requests会比urllib更加方便，能够节约咱们大量的工做。

    requests是python实现的最简单易用的HTTP库，建议爬虫使用requests库。默认安装好python以后，是没有安装requests模块的，须要单独经过pip安装

requests请求

requests模块支持的请求

import requests
requests.get("http://httpbin.org/get")
requests.post("http://httpbin.org/post")
requests.put("http://httpbin.org/put")
requests.delete("http://httpbin.org/delete")
requests.head("http://httpbin.org/get")
requests.options("http://httpbin.org/get")　

GET请求

1 基本请求

res = requests.get('https://www.jd.com/')

with open("jd.html", 'wb') as f:
    f.write(res.content)

2 含参数请求

    params参数指url '?'后的键值对

res = requests.get('https://list.tmall.com/search_product.html')
res = requests.get('https://list.tmall.com/search_product.htm', params={"q": "手机"})

with open('tao_bao.html', 'wb') as f:
     f.write(res.content)

3 含请求头请求

res = requests.get("https://dig.chouti.com/", headers={
        'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/72.0.3626.119 Safari/537.36'
})

with open('chouti.html', 'wb') as f:
    f.write(res.content)

4 含cookies请求

import uuid

res = requests.get("http://httpbin.org/cookies", cookies={'sbid': str(uuid.uuid4()), 'a': '1'})
print(res.text)

5 session对象

session = requests.session()
session.post('/login/')
session.get('/index/')

POST请求

    requests.post()用法与requests.get()彻底一致，特殊的是requests.post()多了一个data参数

1 data参数

    用于存放请求体数据。content-type默认为application/x-www-form-urlencoed，此时请求体数据放于字典'form'键中

res = requests.post('http://httpbin.org/post', params={'a': '10'}, data={'name': 'ethan'})
print(res.text)

2 发送json数据

    此时请求体数据放于字典'data'键中

res1 = requests.post('http://httpbin.org/post', json={'name': 'ethan'})    # 没有指定请求头，默认请求头Content-Type: application/x-www-form-urlencoded
print(res1.json())  

res2 = requests.post('http://httpbin.org/post', json={'age': '24'})    # 默认请求头Content-Type：application/json
print(res2.json())    

代理

    一些网站会有相应的反爬虫措施，例如不少网站会检测某一段时间某个IP的访问次数，若是访问频率太快以致于看起来不像正常访客，它可能就会禁止这个IP的访问。因此咱们须要设置一些代理服务器，每隔一段时间换一个代理，就算IP被禁止，依然能够换个IP继续爬取。

res=requests.get('http://httpbin.org/ip', proxies={'http':'110.83.40.27:9999'}).json()
print(res)

免费代理

response对象

1 常见属性

import requests
respone=requests.get('https://sh.lianjia.com/ershoufang/')
# respone属性
print(respone.text)
print(respone.content)
print(respone.status_code)
print(respone.headers)
print(respone.cookies)
print(respone.cookies.get_dict())
print(respone.cookies.items())
print(respone.url)
print(respone.history)
print(respone.encoding)

2 编码问题

    requests默认编码为ISO-8859-1

res = requests.get('https://www.autohome.com.cn/beijing/')   # 该网站页面内容为gb2312编码的,若是不设置成gbk则中文乱码


# 爬取方式一
with open('autohome.html', 'wb') as f:
    f.write(res.content)


# 爬取方式二
res.encoding = 'gbk'
with open("autohome.html", 'w') as f:
    f.write(res.text)

3 下载二进制文件（图片，视频，音频）

res = requests.get('https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1551350578249&di=23ff7cbf4b8b47fe212e67ba3aab3267&imgtype=0&src=http%3A%2F%2Fimg.hx2cars.com%2Fupload%2Fnewimg2%2FM03%2FA9%2F03%2FClo8xFklT1GAU059AAR1t2rZPz4517_small_800_600.jpg')

with open('c180.jpg', 'wb') as f:
    # f.write(res.content)
    for line in res.iter_content():  # 按行写入
        f.write(line)

4 解析json数据

res = requests.get('http://httpbin.org/get')
print(res.text)
print(type(res.text))    # str

print(res.json())
print(type(res.json()))  # dict

5 Redirection and history

    默认状况下，除了requests.head，requests会自动处理全部重定向。能够使用响应对象的history方法来追踪重定向。

    response.history是一个response对象的列表，为了完成请求而建立了这些对象。这个对象列表按照从最老到最近的请求进行排序

res = requests.get('http://www.jd.com/')
print(res.history)    # [<Response [302]>]
print(res.text)
print(res.status_code)  # 200

    可经过allow_redirects参数禁用重定向处理：

res = requests.get('http://www.jd.com/', allow_redirects=False)
print(res.history)    # []
print(res.status_code)    # 302