爬虫之requests库

爬虫之requests库 爬虫得会requests库吧?示例通俗易懂,5分钟get!

requests库

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虽然Python的标准库中 urllib模块已经包含了平常我们使用的大多数功能,但是它的 API 使用起来让人感觉不太好,而 Requests宣传是 “HTTP for Humans”,说明使用更简洁方便;

Requests 是用Python语言编写,基于 urllib,但是它比 urllib 更加方便,可以节约我们大量的工作,完全满足 HTTP 测试需求;

安装

部分源码

"""
Requests HTTP Library
~~~~~~~~~~~~~~~~~~~~~

Requests is an HTTP library, written in Python, for human beings.
Basic GET usage:

   >>> import requests
   >>> r = requests.get('https://www.python.org')
   >>> r.status_code
   200
   >>> b'Python is a programming language' in r.content
   True

... or POST:

   >>> payload = dict(key1='value1', key2='value2')
   >>> r = requests.post('https://httpbin.org/post', data=payload)
   >>> print(r.text)
   {
     ...
     "form": {
       "key1": "value1",
       "key2": "value2"
     },
     ...
   }

The other HTTP methods are supported - see `requests.api`. Full documentation
is at <https://requests.readthedocs.io>.

:copyright: (c) 2017 by Kenneth Reitz.
:license: Apache 2.0, see LICENSE for more details.
"""

通过源码我们可以发现,主要用法是GET请求和POST请求,介绍了查看状态码和查看文本等方法,其他HTTP请求方法查看request.api,常用的方法用法如下:

发送GET请求

URL 的查询字符串(query string)传递某种数据,我们可以通过params参数来传递,requests库不需要url编码,自动给我们编码处理

import requests

url = "http://httpbin.org/get"
payload = {'key':'value','key2':'value'}
r = requests.get(url,params=payload)
print(r.text)
print(r.url) # http://httpbin.org/get?key=value&key2=value

列表作为值传入:

payload = {'key1': 'value1', 'key2': ['value2', 'value3']}

r = requests.get('http://httpbin.org/get', params=payload)
 print(r.url)
http://httpbin.org/get?key1=value1&key2=value2&key2=value3

ps:注意字典里值为 None 的键都不会被添加到 URL 的查询字符串里。

import requests

# 添加headers参数
headers = {
'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.86 Safari/537.36'
}
# https://www.baidu.com/s?&word=%E4%B8%AD%E5%9B%BD
url = 'https://www.baidu.com/s'
kw = {'wd':'中国'}

# # params 接收一个字典或者字符串的查询参数,字典类型自动转换为url编码,不需要urlencode()
response = requests.get(url,headers=headers,params=kw)
print(response) # <Response [200]>

'''更多属性方法'''
# print(response.text)  # 返回unicode格式的数据
print(response.content)  # 返回字节流数据
print(response.status_code)  # 200
print(response.url) # https://www.baidu.com/s?wd=%E4%B8%AD%E5%9B%BD  查看完整url地址
print(response.encoding) # utf-8

response.text和response.content的区别:

  1. response.content :这个是直接从网络上抓取的数据,没有经过任何的编码,所以是一个bytes类型,其实在硬盘上和网络上传输的字符串都是bytes类型
  2. response.text:这个是str的数据类型,是requests库将response.content进行解码的字符串,解码需要指定一个编码方式,requests会根据自己的猜测来判断编码的方式,所以有时候可能会猜测错误,就会导致解码产生乱码,这时候就应该进行手动解码,比如使用response.content.decode('utf8')

发送POST请求

r = requests.post('http://httpbin.org/post', data = {'key':'value'})
import requests

url = 'https://i.meishi.cc/login.php?redirect=https%3A%2F%2Fwww.meishij.net%2F'
headers={
    'User-Agent':'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.86 Safari/537.36'
}
data = {
    'redirect': 'https://www.meishij.net/',
    'username': '1097566154@qq.com',
    'password': 'wq15290884759.'
}
resp = requests.post(url,headers=headers,data=data)
print(resp.text)

Requests 简便的 API 意味着所有 HTTP 请求类型都是显而易见的,那么其他 HTTP 请求类型:PUT,DELETE,HEAD 以及 OPTIONS 又是如何的呢?都是一样的简单:

>>> r = requests.put('http://httpbin.org/put', data = {'key':'value'})
>>> r = requests.delete('http://httpbin.org/delete')
>>> r = requests.head('http://httpbin.org/get')
>>> r = requests.options('http://httpbin.org/get')

requests使用代理

只要在请求的方法中(比如get或者post)传递proxies参数就可以了

import requests

proxy = {
    'http':'111.77.197.127:9999'
}
url = 'http://www.httpbin.org/ip'
resp = requests.get(url,proxies=proxy)
print(resp.text)

如果在一个响应中包含了cookie,那么可以利用cookies属性拿到这个返回的cookie值

import requests

resp = requests.get('http://www.baidu.com/')
print(resp.cookies)
print(resp.cookies.get_dict())

Cookie模拟登录

import requests
url = 'https://www.zhihu.com/hot'
headers = {
    'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.86 Safari/537.36',
    'cookie':'_zap=59cde9c3-c5c0-4baa-b756-fa16b5e72b10; d_c0="APDi1NJcuQ6PTvP9qa1EKY6nlhVHc_zYWGM=|1545737641"; __gads=ID=237616e597ec37ad:T=1546339385:S=ALNI_Mbo2JturZesh38v7GzEeKjlADtQ5Q; _xsrf=pOd30ApWQ2jihUIfq94gn2UXxc0zEeay; q_c1=1767e338c3ab416692e624763646fc07|1554209209000|1545743740000; tst=h; __utma=51854390.247721793.1554359436.1554359436.1554359436.1; __utmc=51854390; __utmz=51854390.1554359436.1.1.utmcsr=zhihu.com|utmccn=(referral)|utmcmd=referral|utmcct=/hot; __utmv=51854390.100-1|2=registration_date=20180515=1^3=entry_date=20180515=1; l_n_c=1; l_cap_id="OWRiYjI0NzJhYzYwNDM3MmE2ZmIxMGIzYmQwYzgzN2I=|1554365239|875ac141458a2ebc478680d99b9219c461947071"; r_cap_id="MmZmNDFkYmIyM2YwNDAxZmJhNWU1NmFjOGRkNDNjYjc=|1554365239|54372ab1797cba8c4dd224ba1845dd7d3f851802"; cap_id="YzQwNGFlYWNmNjY3NDFhNGI4MGMyYjZjYjRhMzQ1ZmE=|1554365239|385cc25e3c4e3b0b68ad5747f623cf3ad2955c9f"; n_c=1; capsion_ticket="2|1:0|10:1554366287|14:capsion_ticket|44:MmE5YzNkYjgzODAyNDgzNzg5MTdjNmE3NjQyODllOGE=|40d3498bedab1b7ba1a247d9fc70dc0e4f9a4f394d095b0992a4c85e32fd29be"; z_c0="2|1:0|10:1554366318|4:z_c0|92:Mi4xOWpCeUNRQUFBQUFBOE9MVTBseTVEaVlBQUFCZ0FsVk5iZzJUWFFEWi1JMkxnQXlVUXh2SlhYb3NmWks3d1VwMXRB|81b45e01da4bc235c2e7e535d580a8cc07679b50dac9e02de2711e66c65460c6"; tgw_l7_route=578107ff0d4b4f191be329db6089ff48'
}
resp = requests.get(url,headers=headers)
print(resp.text)

Session:共享cookie

使用requests,也要达到共享cookie的目的,那么可以使用requests库给我们提供的session对象;

注意:这里的session不是web开发中的那个session,这个地方只是一个会话的对象而已

import requests

# 登录链接
post_url = 'https://i.meishi.cc/login.php?redirect=https%3A%2F%2Fwww.meishij.net%2F'
post_data = {
    'username':'1097566154@qq.com',
    'password':'wq15290884759.'
}
headers={
    'User-Agent':'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.86 Safari/537.36'
}

# 登录
# 通过session方法创建一个会话对象
session = requests.session()
# 发送post请求,携带登录数据
session.post(post_url,headers=headers,data=post_data)

'''有了cookie信息,访问个人网页'''
url = 'https://i.meishi.cc/cook.php?id=13686422'

resp = session.get(url)
print(resp.text)

处理不信任的SSL证书:

对于那些已经被信任的SSL证书的网站,比如https://www.baidu.com/,那么使用requests直接就可以正常的返回响应;

如果是自签证书,那么浏览器是不承认该证书的,提示不安全,那么在爬取的时候会报错,需要怎么处理?添加verify=False参数

示例代码如下:

resp = requests.get('https://inv-veri.chinatax.gov.cn/',verify=False)
print(resp.content.decode('utf-8'))
# 之前网站,有些没有认证过的ssl证书,我们访问需要手动携带证书
# 跳过证书直接访问
import requests
respone=requests.get('https://www.12306.cn',verify=False) #不验证证书,报警告,返回200
print(respone.status_code)
# 手动携带
import requests
respone=requests.get('https://www.12306.cn',
                     cert=('/path/server.crt',
                           '/path/key'))
print(respone.status_code)

响应对象

## 响应对象
import requests
respone=requests.get('http://www.jianshu.com')
# respone属性
print(respone.text)  # 返回响应体的文本内容
print(respone.content)# 返回响应体的二进制内容

print(respone.status_code)# 响应状态码
print(respone.headers)# 响应头
print(respone.cookies)# 响应的cookie
print(respone.cookies.get_dict())# 响应的cookie转成字典
print(respone.cookies.items())

print(respone.url) # 请求地址
print(respone.history) # 了解---》如果有重定向,列表,放着重定向之前的地址

print(respone.encoding) # 页面的编码方式:utf-8   gbk
# response.iter_content()  # content迭代取出content二进制内容,一般用它存文件

'''
编码问题:response.encoding='gbk'
'''

获取二进制数据

# 下载图片
header={
    'user-agent': 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/99.0.4844.74 Safari/537.36'
}

res=requests.get('https://tva1.sinaimg.cn/mw2000/9d52c073gy1h1v6lmny8nj20j60pjtdh.jpg',headers=header)
with open('mv.jpg','wb') as f:
    # f.write(res.content)
    for line in res.iter_content(100):
        f.write(line)

解析json

import json

data = {
    'cname': '',
    'pid': '',
    'keyword': '上海',
    'pageIndex': 1,
    'pageSize': 10,
}

# 方式一:
# res = requests.post('http://www.kfc.com.cn/kfccda/ashx/GetStoreList.ashx?op=keyword',data=data)
# j = json.loads(res.text)
# print(j['Table'][0]['rowcount'])

# 方式二:
res= requests.post('http://www.kfc.com.cn/kfccda/ashx/GetStoreList.ashx?op=keyword',data=data).json()
print(res['Table'][0]['rowcount'])

Requests 2.18.1 文档 (python-requests.org)

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