引入

在学习爬虫之前可以先大致的了解一下HTTP协议~

HTTP协议：https://www.cnblogs.com/peng104/p/9846613.html

爬虫的基本流程

简介

简介：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它会比urllib更加方便，可以节约我们大量的工作。一句话，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之后，是没有安装requests模块的，需要单独通过pip安装

安装方法：pip install requests

开源地址：https://github.com/kennethreitz/requests
中文文档 API： http://docs.python-requests.org/zh_CN/latest/index.html

基本语法

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

import requests
response=requests.get(‘https://www.jd.com/‘,)

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

2. 含参数请求

import requests
response=requests.get(‘https://s.taobao.com/search?q=手机‘)
response=requests.get(‘https://s.taobao.com/search‘,params={"q":"三只松鼠"})

3. 含请求头

import requests
response=requests.get(‘https://dig.chouti.com/‘,
             headers={
                   ‘User-Agent‘:‘Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/62.0.3202.75 Safari/537.36‘,
                         }
                      )

4. 含cookies请求

import uuid
import requests

url = ‘http://httpbin.org/cookies‘
cookies = dict(sbid=str(uuid.uuid4()))

res = requests.get(url, cookies=cookies)
print(res.text)

5. request.session()

import requests

session=requests.session()
res1=session.get("https://www.zhihu.com/explore")
print(session.cookies.get_dict())
res2=session.get("https://www.zhihu.com/question/30565354/answer/463324517",cookies={"abs":"123"}

post请求

1. data参数
requests.post()用法与requests.get()完全一致，特殊的是requests.post()多了一个data参数，用来存放请求体数据

response=requests.post("http://httpbin.org/post",params={"a":"10"}, data={"name":"peng"})

2. 发送json数据

import requests
res1=requests.post(url=‘http://httpbin.org/post‘, data={‘name‘:‘yuan‘}) #没有指定请求头,#默认的请求头:application/x-www-form-urlencoed
print(res1.json())

res2=requests.post(url=‘http://httpbin.org/post‘,json={‘age‘:"22",}) #默认的请求头:application/json
print(res2.json())

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

import requests
response=requests.get(‘http://www.autohome.com/news‘)
#response.encoding=‘gbk‘ #汽车之家网站返回的页面内容为gb2312编码的，而requests的默认编码为ISO-8859-1，如果不设置成gbk则中文乱码
with open("res.html","w") as f:
    f.write(response.text)

3. 下载二进制文件（图片，视频，音频）

import requests
response=requests.get(‘http://bangimg1.dahe.cn/forum/201612/10/200447p36yk96im76vatyk.jpg‘)
with open("res.png","wb") as f:
    # f.write(response.content) # 比如下载视频时,如果视频100G,用response.content然后一下子写到文件中是不合理的
    for line in response.iter_content():
        f.write(line)

4. 解析json数据

import requests
import json

response=requests.get(‘http://httpbin.org/get‘)
res1=json.loads(response.text) #太麻烦
res2=response.json() #直接获取json数据
print(res1==res2)

5. Redirection and History

默认情况下，除了 HEAD, Requests 会自动处理所有重定向。可以使用响应对象的 history 方法来追踪重定向。Response.history 是一个 Response 对象的列表，为了完成请求而创建了这些对象。这个对象列表按照从最老到最近的请求进行排序。

>>> r = requests.get(‘http://github.com‘)
>>> r.url
‘https://github.com/‘
>>> r.status_code
200
>>> r.history
[<Response [301]>]

另外，还可以通过 allow_redirects 参数禁用重定向处理：

>>> r = requests.get(‘http://github.com‘, allow_redirects=False)
>>> r.status_code
301
>>> r.history
[]　

进阶用法

proxies代理

免费代理

如果需要使用代理，你可以通过为任意请求方法提供 proxies 参数来配置单个请求：

import requests

# 根据协议类型，选择不同的代理
proxies = {
  "http": "http://12.34.56.79:9527",
  "https": "http://12.34.56.79:9527",
}

response = requests.get("http://www.baidu.com", proxies = proxies)
print(response.text)

也可以通过本地环境变量 HTTP_PROXY 和 HTTPS_PROXY 来配置代理：

export HTTP_PROXY="http://12.34.56.79:9527"
export HTTPS_PROXY="https://12.34.56.79:9527"

私密代理

import requests

# 如果代理需要使用HTTP Basic Auth，可以使用下面这种格式：
proxy = { "http": "mr_mao_hacker:[email protected]:16816" }

response = requests.get("http://www.baidu.com", proxies = proxy)

print(response.text)

web客户端验证

如果是Web客户端验证，需要添加 auth = (账户名, 密码)

import requests

auth=(‘test‘, ‘123456‘)

response = requests.get(‘http://192.168.199.107‘, auth = auth)

print(response.text)

两个栗子

1、模拟GitHub登录，获取登录信息

import requests
import re

#请求1:
r1=requests.get(‘https://github.com/login‘)
r1_cookie=r1.cookies.get_dict() #拿到初始cookie(未被授权)
authenticity_token=re.findall(r‘name="authenticity_token".*?value="(.*?)"‘,r1.text)[0] #从页面中拿到CSRF TOKEN
print("authenticity_token",authenticity_token)
#第二次请求：带着初始cookie和TOKEN发送POST请求给登录页面，带上账号密码
data={
    ‘commit‘:‘Sign in‘,
    ‘utf8‘:‘?‘,
    ‘authenticity_token‘:authenticity_token,
    ‘login‘:‘你的github账号？‘,
    ‘password‘:‘你的密码‘
}

#请求2:
r2=requests.post(‘https://github.com/session‘,
             data=data,
             cookies=r1_cookie,
             # allow_redirects=False
             )
print(r2.status_code)      #200
print(r2.url)              #看到的是跳转后的页面:https://github.com/
print(r2.history)          #看到的是跳转前的response:[<Response [302]>]
print(r2.history[0].text)  #看到的是跳转前的response.text

with open("result.html","wb") as f:

    f.write(r2.content)

2、爬取豆瓣电影信息

import requests

import re
import json
import time
from concurrent.futures import ThreadPoolExecutor
pool=ThreadPoolExecutor(50)

def getPage(url):

    response=requests.get(url)
    return response.text

def parsePage(res):

    com=re.compile(‘<div class="item">.*?<div class="pic">.*?<em .*?>(?P<id>\d+).*?<span class="title">(?P<title>.*?)</span>‘
                   ‘.*?<span class="rating_num" .*?>(?P<rating_num>.*?)</span>.*?<span>(?P<comment_num>.*?)评价</span>‘,re.S)

    iter_result=com.finditer(res)

    return iter_result

def gen_movie_info(iter_result):
    for i in iter_result:
        yield {
            "id":i.group("id"),
            "title":i.group("title"),
            "rating_num":i.group("rating_num"),
            "comment_num":i.group("comment_num"),
        }

def stored(gen):
        with open("move_info.txt","a",encoding="utf8") as f:
            for line in gen:
                data=json.dumps(line,ensure_ascii=False)
                f.write(data+"\n")

def spider_movie_info(url):
    res=getPage(url)
    iter_result=parsePage(res)
    gen=gen_movie_info(iter_result)
    stored(gen)

def main(num):

    url=‘https://movie.douban.com/top250?start=%s&filter=‘%num
    pool.submit(spider_movie_info,url)
    #spider_movie_info(url)

if __name__ == ‘__main__‘:
    before=time.time()
    count=0
    for i in range(10):
        main(count)
        count+=25
    after=time.time()

    print("总共耗费时间：",after-before)

原文地址：https://www.cnblogs.com/peng104/p/10311846.html