python scrapy爬虫 app scrapy 全网爬虫

转载

mob6454cc6df18d 2024-01-29 06:05:17

文章标签 python scrapy爬虫 app python全站爬虫 ide 中间件 sql 文章分类 Python 后端开发

Scrapy是一个为了爬取网站数据，提取结构性数据而编写的应用框架。其可以应用在数据挖掘，信息处理或存储历史数据等一系列的程序中。

其最初是为了页面抓取 (更确切来说, 网络抓取 )所设计的，也可以应用在获取API所返回的数据(例如 Amazon Associates Web Services ) 或者通用的网络爬虫。Scrapy用途广泛，可以用于数据挖掘、监测和自动化测试。

Scrapy 使用了 Twisted异步网络库来处理网络通讯。整体架构大致如下

Scrapy主要包括了以下组件：

引擎(Scrapy)

用来处理整个系统的数据流处理, 触发事务(框架核心)

调度器(Scheduler)

用来接受引擎发过来的请求, 压入队列中, 并在引擎再次请求的时候返回. 可以想像成一个URL(抓取网页的网址或者说是链接)的优先队列, 由它来决定下一个要抓取的网址是什么, 同时去除重复的网址

下载器(Downloader)

用于下载网页内容, 并将网页内容返回给蜘蛛(Scrapy下载器是建立在twisted这个高效的异步模型上的)

爬虫(Spiders)

爬虫是主要干活的, 用于从特定的网页中提取自己需要的信息, 即所谓的实体(Item)。用户也可以从中提取出链接,让Scrapy继续抓取下一个页面

项目管道(Pipeline)

负责处理爬虫从网页中抽取的实体，主要的功能是持久化实体、验证实体的有效性、清除不需要的信息。当页面被爬虫解析后，将被发送到项目管道，并经过几个特定的次序处理数据。

下载器中间件(Downloader Middlewares)

位于Scrapy引擎和下载器之间的框架，主要是处理Scrapy引擎与下载器之间的请求及响应。

爬虫中间件(Spider Middlewares)

介于Scrapy引擎和爬虫之间的框架，主要工作是处理蜘蛛的响应输入和请求输出。

调度中间件(Scheduler Middewares)

介于Scrapy引擎和调度之间的中间件，从Scrapy引擎发送到调度的请求和响应。

Scrapy运行流程大概如下：

引擎从调度器中取出一个链接(URL)用于接下来的抓取

引擎把URL封装成一个请求(Request)传给下载器

下载器把资源下载下来，并封装成应答包(Response)

爬虫解析Response

解析出实体(Item),则交给实体管道进行进一步的处理

解析出的是链接(URL),则把URL交给调度器等待抓取

以下实现的一个简单的简书全站爬虫，并存储到mysql数据库

# -*- coding: utf-8 -*-
"""
js.py
"""
import scrapy
import json
from scrapy.linkextractors import LinkExtractor
from scrapy.spiders import CrawlSpider, Rule
from ..items import Article, Author
class JsSpider(CrawlSpider):
name = 'js'
allowed_domains = ['jianshu.com']
start_urls = ['http://jianshu.com/']
rules = (
Rule(LinkExtractor(allow=r'.*/p/[0-9a-z]{12}.*'), callback='parse_detail', follow=True),
)
def parse_detail(self, response):
title = response.xpath('//h1[@class="title"]/text()').get()
content = response.xpath('//div[@class="show-content"]').get()
origin_url = response.url.split("?")[0]
article_id = origin_url.split("/")[-1]
author1 = response.xpath('//span[@class="name"]/a/text()').get()
avatar = response.xpath('//a[@class="avatar"]/img/@src').get()
page_date = response.xpath('//script[@data-name="page-data"]/text()').get()
data = json.loads(page_date)
pub_time = response.xpath('//span[@class="publish-time"]/text()').get().split()[0]
word_num = data.get("public_wordage")
read_num = data.get("views_count")
comment_num = data.get("comments_count")
likes_num = data.get("likes_count")
rewards_num = data.get("total_rewards_count")
article = Article(title=title,
content=content,
origin_url=origin_url,
article_id=article_id,
author=author1,
avatar=avatar)
yield article
"""
items.py
"""
import scrapy
from scrapy import Field
class Article(scrapy.Item):
title = Field()
content = Field()
article_id = Field()
author = Field()
origin_url = Field()
avatar = Field()
class Author(scrapy.Item):
nickname = Field()
total_likes_count = Field()
total_wordage = Field()
followers_count = Field()
# -*- coding: utf-8 -*-
"""
DownloaderMiddlewar:下载中间件
SpiderMiddleware：爬虫中间件
engine-->调度器--->request--->下载中间件--->response--->spider
-->爬虫中间件-->(pipeline持久化或者engine)
内置下载中间件
{
'scrapy.contrib.downloadermiddleware.robotstxt.RobotsTxtMiddleware': 100,
'scrapy.contrib.downloadermiddleware.httpauth.HttpAuthMiddleware': 300,
'scrapy.contrib.downloadermiddleware.downloadtimeout.DownloadTimeoutMiddleware': 350,
'scrapy.contrib.downloadermiddleware.useragent.UserAgentMiddleware': 400,
'scrapy.contrib.downloadermiddleware.retry.RetryMiddleware': 500,
'scrapy.contrib.downloadermiddleware.defaultheaders.DefaultHeadersMiddleware': 550,
'scrapy.contrib.downloadermiddleware.redirect.MetaRefreshMiddleware': 580,
'scrapy.contrib.downloadermiddleware.httpcompression.HttpCompressionMiddleware': 590,
'scrapy.contrib.downloadermiddleware.redirect.RedirectMiddleware': 600,
'scrapy.contrib.downloadermiddleware.cookies.CookiesMiddleware': 700,
'scrapy.contrib.downloadermiddleware.httpproxy.HttpProxyMiddleware': 750,
'scrapy.contrib.downloadermiddleware.chunked.ChunkedTransferMiddleware': 830,
'scrapy.contrib.downloadermiddleware.stats.DownloaderStats': 850,
'scrapy.contrib.downloadermiddleware.httpcache.HttpCacheMiddleware': 900,
}
内置爬虫中间件：
'scrapy.contrib.spidermiddleware.httperror.HttpErrorMiddleware': 50,
'scrapy.contrib.spidermiddleware.offsite.OffsiteMiddleware': 500,
'scrapy.contrib.spidermiddleware.referer.RefererMiddleware': 700,
'scrapy.contrib.spidermiddleware.urllength.UrlLengthMiddleware': 800,
'scrapy.contrib.spidermiddleware.depth.DepthMiddleware': 900,
"""
from scrapy import signals
class JianshuSpiderSpiderMiddleware(object):
# Not all methods need to be defined. If a method is not defined,
# scrapy acts as if the spider middleware does not modify the
# passed objects.
@classmethod
def from_crawler(cls, crawler):
# This method is used by Scrapy to create your spiders.
s = cls()
crawler.signals.connect(s.spider_opened, signal=signals.spider_opened)
return s
def process_spider_input(self, response, spider):
# Called for each response that goes through the spider
# middleware and into the spider.
#下载完成，response交给spider
# Should return None or raise an exception.
return None
def process_spider_output(self, response, result, spider):
# Called with the results returned from the Spider, after
# it has processed the response.
#spider执行完成以后执行
# Must return an iterable of Request, dict or Item objects.
for i in result:
yield i
def process_spider_exception(self, response, exception, spider):
# Called when a spider or process_spider_input() method
# (from other spider middleware) raises an exception.
# Should return either None or an iterable of Response, dict
# or Item objects.
pass
def process_start_requests(self, start_requests, spider):
# Called with the start requests of the spider, and works
# similarly to the process_spider_output() method, except
# that it doesn’t have a response associated.
#爬虫启动时调用
# Must return only requests (not items).
for r in start_requests:
yield r
def spider_opened(self, spider):
spider.logger.info('Spider opened: %s' % spider.name)
class JianshuSpiderDownloaderMiddleware(object):
# Not all methods need to be defined. If a method is not defined,
# scrapy acts as if the downloader middleware does not modify the
# passed objects.
@classmethod
def from_crawler(cls, crawler):
# This method is used by Scrapy to create your spiders.
s = cls()
crawler.signals.connect(s.spider_opened, signal=signals.spider_opened)
return s
def process_request(self, request, spider):
# Called for each request that goes through the downloader
# middleware.
# Must either:
# - return None: continue processing this request后续中间件继续下载
# - or return a Response object停止process_request，开始执行process_response
# - or return a Request object停止中间件，重新调度Request
# - or raise IgnoreRequest: process_exception() methods 执行process_exception
# installed downloader middleware will be called
return None
def process_response(self, request, response, spider):
# Called with the response returned from the downloader.
# Must either;
# - return a Response object
# - return a Request object
# - or raise IgnoreRequest
return response
def process_exception(self, request, exception, spider):
# Called when a download handler or a process_request()
# (from other downloader middleware) raises an exception.
# Must either:
# - return None: continue processing this exception
# - return a Response object: stops process_exception() chain
# - return a Request object: stops process_exception() chain
pass
def spider_opened(self, spider):
spider.logger.info('Spider opened: %s' % spider.name)
下面是持久化数据的操作，使用的是twisetd支持的异步引擎提高存储速度,并且数据库相关配置信息从setting文件里面读取：
# -*- coding: utf-8 -*-
"""
pipeline.py
"""
# Define your item pipelines here
#
# Don't forget to add your pipeline to the ITEM_PIPELINES setting
# See: https://doc.scrapy.org/en/latest/topics/item-pipeline.html
from twisted.enterprise import adbapi
from pymysql import cursors
class JianshuSpiderPipeline(object):
def __init__(self, conn):
self.conn = conn
self.conn.update({'cursorclass':cursors.DictCursor})
print('===========>',self.conn)
self.dbpool = adbapi.ConnectionPool('pymysql', **self.conn)
self._sql = None
@classmethod
def from_crawler(cls, crawler):#创建对象读取配置文件
conn_info = crawler.settings.get('DB')
return cls(conn_info)
@property
def sql(self):
if not self._sql:
# self._sql = """insert into article(id, title, content, article_id, author, origin_url, avatar) values(null, %s, %s, %s, %s, %s，%s)"""
self._sql = """insert into article(id, title, content, article_id, author, origin_url) values(null, %s, %s, %s, %s, %s)"""
return self._sql
def process_item(self, item, spider):
defer = self.dbpool.runInteraction(self._insert_item, item)
defer.addErrback(self._handle_error, item, spider)
return item #交给下一个pipeline
# from scrapy.exceptions import DropItem
# raise DropItem()#丢弃(信号可以捕捉到)，不给下一个pipeline
def _insert_item(self, cursor, item):
params = (item['title'],
item['content'],
item['article_id'],
item['author'],
item['origin_url']
)
cursor.execute(self.sql, params)
def _handle_error(self, failue, item, spider):
print('failue=====>', failue)
def open_spider(self, spider):
pass
def close_spider(self, spider):
pass
下面是setting配置文件，里面有部分配置的注释
# -*- coding: utf-8 -*-
# Scrapy settings for jianshu_spider project
#
# For simplicity, this file contains only settings considered important or
# commonly used. You can find more settings consulting the documentation:
#
# https://doc.scrapy.org/en/latest/topics/settings.html
# https://doc.scrapy.org/en/latest/topics/downloader-middleware.html
# https://doc.scrapy.org/en/latest/topics/spider-middleware.html
BOT_NAME = 'jianshu_spider'
SPIDER_MODULES = ['jianshu_spider.spiders']
NEWSPIDER_MODULE = 'jianshu_spider.spiders'
# Crawl responsibly by identifying yourself (and your website) on the user-agent
#USER_AGENT = 'jianshu_spider (+http://www.yourdomain.com)'
# Obey robots.txt rules
#ROBOTSTXT_OBEY = True
# Configure maximum concurrent requests performed by Scrapy (default: 16)
#CONCURRENT_REQUESTS = 32 #最大发送请求数量，，默认16
# Configure a delay for requests for the same website (default: 0)
# See https://doc.scrapy.org/en/latest/topics/settings.html#download-delay
# See also autothrottle settings and docs
DOWNLOAD_DELAY = 3 #访问频率控制(s)
# The download delay setting will honor only one of:
#CONCURRENT_REQUESTS_PER_DOMAIN = 16每个域名最多发送请求数量
#CONCURRENT_REQUESTS_PER_IP = 16每个ip并发数量
# Disable cookies (enabled by default)
#COOKIES_ENABLED = False请求携带cookie
#COOKIES_DEBUG = False
# Disable Telnet Console (enabled by default)
#TELNETCONSOLE_ENABLED = False#监听爬虫当前状态和指标，开始暂停等
# Override the default request headers:
DEFAULT_REQUEST_HEADERS = {
'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
'Accept-Language': 'en',
'User-Agent':'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36'
}
# Enable or disable spider middlewares
# See https://doc.scrapy.org/en/latest/topics/spider-middleware.html
#SPIDER_MIDDLEWARES = {
# 'jianshu_spider.middlewares.JianshuSpiderSpiderMiddleware': 543,
#}
# Enable or disable downloader middlewares
# See https://doc.scrapy.org/en/latest/topics/downloader-middleware.html
#DOWNLOADER_MIDDLEWARES = {
# 'jianshu_spider.middlewares.JianshuSpiderDownloaderMiddleware': 543,
#}
# Configure item pipelines
# See https://doc.scrapy.org/en/latest/topics/item-pipeline.html
ITEM_PIPELINES = {
'jianshu_spider.pipelines.JianshuSpiderPipeline': 300,
}
# Enable and configure the AutoThrottle extension (disabled by default)
# See https://doc.scrapy.org/en/latest/topics/autothrottle.html
#智能模拟请求，限速
#AUTOTHROTTLE_ENABLED = True
# The initial download delay
#AUTOTHROTTLE_START_DELAY = 5
# The maximum download delay to be set in case of high latencies
#AUTOTHROTTLE_MAX_DELAY = 60
# The average number of requests Scrapy should be sending in parallel to
# each remote server
#AUTOTHROTTLE_TARGET_CONCURRENCY = 1.0
# Enable showing throttling stats for every response received:
#AUTOTHROTTLE_DEBUG = False
# Enable and configure HTTP caching (disabled by default)
# See https://doc.scrapy.org/en/latest/topics/downloader-middleware.html#httpcache-middleware-settings
#HTTPCACHE_ENABLED = True启用缓存(这个地方可以自定义)
#HTTPCACHE_EXPIRATION_SECS = 0#超时时间
#HTTPCACHE_DIR = 'httpcache'#缓存目录
#HTTPCACHE_IGNORE_HTTP_CODES = []#忽略的状态码
#HTTPCACHE_STORAGE = 'scrapy.extensions.httpcache.FilesystemCacheStorage'#所有请求都缓存
#定义爬取深度
DEPTH_LIMIT = 2
DEPTH_PRIORITY = 0#广度或者深度优先
#自定义去重方式
#默认方式DUPEFILTER_CLASS = "scrapy.dupefilters.RFPDupeFilter"
DUPEFILTER_CLASS = "jianshu_spider.duplication.RepeatFilter"
##########DB setting ############
DB = { #key务必大写
'host': '127.0.0.1',
'port': 3306,
'user' : 'root',
'password' : 'pwd',
'database' : 'jianshu',
'charset' : 'utf8'
}
##########扩展钩子################
# from scrapy.extensions import telnet 扩展实例
# from scrapy import signals 扩展汇总
# EXTENSIONS={
# 'jianshu_spider.extensions.MyExtend':300
# }
# Enable or disable extensions
# See https://doc.scrapy.org/en/latest/topics/extensions.html
#EXTENSIONS = {
# 'scrapy.extensions.telnet.TelnetConsole': None,
#}
这里自定义了一个去重的方式，主要是为了学习这里去重的原理，自定义去重后需要在配置文件定义
# -*- coding: utf-8 -*-
"""
dont_filter=False 默认基于内存或者文件去重
from scrapy.dupefilters import RFPDupeFilter
自定义去重也可以基于数据库操作
open:可以加入数据库操作
close:关闭数据库操作
"""
from scrapy.dupefilters import BaseDupeFilter
class RepeatFilter(BaseDupeFilter):
"""Request Fingerprint duplicates filter"""
def __init__(self):
self.visited_set = set()
@classmethod
def from_settings(cls, settings):
return cls()
def request_seen(self, request):
if request.url in self.visited_set:
return True
self.visited_set.add(request.url)
return False
def open(self):
pass
def close(self, reason):
pass

启动爬虫，可以看到数据库已经开始存入数据：

本文章为转载内容，我们尊重原作者对文章享有的著作权。如有内容错误或侵权问题，欢迎原作者联系我们进行内容更正或删除文章。