scrapy使用指南

创建scrapy项目:

scrapy startproject 项目名

cd到项目名下

scrapy genspider 爬虫名 www.baidu.com(网站网址)

之后按照提示创建爬虫文件（官方测试网站为http://quotes.toscrape.com/）

创建启动文件

from scrapy.cmdline import execute
execute(['scrapy','crawl','quotes'])

quotes是爬虫名，该文件创建在scrapy项目根目录下

css选择器:

response.css('.text::text').extract()

这里为提取所有带有class=’text’ 这个属性的元素里面的text返回的是一个列表

response.css('.text::text').extract_first()

这是取第一条，返回的是str

print(response.css("div span::attr(class)").extract())

这是取元素

Xpath选择器:

url = response.url+response.xpath('/html/body/div/div[2]/div[1]/div[1]/div/a[1]/@href').extract_first()

和原来用法基本一样，这里是获取一个url 然后跟网站的主url拼接了

print(response.xpath("//a[@class='tag']/text()").extract())

取带有class=’tag’属性的超链接中间的文本内容

print(response.url)
print(response.status)

打印该请求的url,打印请求的状态码

保存为json形式的东西

scrapy crawl quotes -o quotes.json

json lines存储

scrapy crawl quotes -o quotes.jl

scrapy crawl quotes -o quotes.csv

scrapy crawl quotes -o quotes.xml

scrapy crawl quotes -o quotes.pickle

scrapy crawl quotes -o quotes.marshal

scrapy crawl quotes -o ftp://user:pass@ftp.example.com/path/to/quotes.csv

piplines.py中的操作

from scrapy.exceptions import DropItem
class HelloPipeline(object):
    def __init__(self):
        self.limit = 50
    def process_item(self,item,spider):
        if item['name']:
            if len(item['name']) > self.limit:
                item['name'] = item['name'][:self.limit].rstrip()+'。。。'
            return item
        else:
            return DropItem

import pymongo
class MongoPipline(object):
    def __init__(self,mongo_url,mongo_db):
        self.mongo_url = mongo_url
        self.mongo_db = mongo_db
    @classmethod
    def from_crawler(cls,crawler):
        return cls(mongo_url=crawler.settings.get('MONGO_URI'),mongo_db=crawler.settings.get('MONGO_DB'))

    def open_spider(self,spider):
        print(self.mongo_url,self.mongo_db)
        self.client = pymongo.MongoClient(self.mongo_url)
        self.db = self.client[self.mongo_db]

    def process_item(self,item,spider):
        self.db['name'].insert(dict(item))
        print(item)
        return item

    def close_spider(self,spider):
        self.client.close()

记得开setting.py：

ITEM_PIPELINES = {
   'hello.pipelines.HelloPipeline': 300,
   'hello.pipelines.MongoPipline': 400,
}

MONGO_URI = '127.0.0.1'
MONGO_DB = 'hello'

DownloadMiddleware

核心方法:

Process_request(self,request,spider)

Return None：继续处理这个request，直到返回response,通常用来修改request

Return Response 直接返回该response

Return Request 将返回的request 重新放归调度队列，当成一个新的request用

Return IgnoreRequest 抛出异常，process_exception被一次调用，

Process_response(self,request,response,spider)

Return request将返回的request 重新放归调度队列，当成一个新的request用

Return response 继续处理该response直到结束

Process_exception(request,excetion,spider)

Return IgnoreRequest 抛出异常，process_exception被一次调用，

通过重写中间件给request加useragent,将返回的状态码都改成201

在setting里:

DOWNLOADER_MIDDLEWARES = {
   'dingdian.middlewares.AgantMiddleware': 543,
}

在middleware里:

import random
class AgantMiddleware(object):
    def __init__(self):
        self.user_agent
= ['Mozilla/5.0 (Windows NT 10.0; WOW64;
rv:58.0) Gecko/20100101 Firefox/58.0']
    def process_request(self,request,spider):
        request.headers['User-Agent'] = random.choice(self.user_agent)
        print(request.headers)

def process_response(self,request,response,spider):
        response.status=201
        return response

scrapy两种请求方式

一种

import scrapy

yield scrapy.Request(begin_url,self.first)

第二种

from scrapy.http import Request

yield Request(url,self.first,meta={'thename':pic_name[0]})

使用post请求的方法:

from scrapy import FormRequest
##Scrapy中用作登录使用的一个包

formdata = {
    'username': 'wangshang',
    'password': 'a706486'
}
yield scrapy.FormRequest(
    url='http://172.16.10.119:8080/bwie/login.do',
    formdata=formdata,
    callback=self.after_login,
)

中间键添加代理IP以及header头

class UserAgentMiddleware(object):
    def __init__(self):
        self.user_agent
= ['Mozilla/5.0 (Windows NT 10.0; Win64; x64)
AppleWebKit/537.36 (KHTML, like Gecko) Chrome/66.0.3359.117 Safari/537.36','Mozilla/5.0
(Windows NT 10.0; WOW64; rv:58.0) Gecko/20100101 Firefox/58.0']
    def process_request(self,request,spider):
        request.meta['proxy'] = 'http://'+'175.42.123.111:33995'