初识爬虫-scrapy框架

摘要

学习心得

经过几天路飞学院爬虫课程的学习,了解了爬虫的本质以及相关的基本知识,今天开始学习爬虫框架scrapy。

前两天的课程学习中应用的是requests和bs4模块,scrapy框架与这两个模块相比无论是速度还是在便捷性上提高的不是一点半点,但是前两天的学习并不是无用的。

前两天的学习了解到整个爬虫的思想以及流程,还有理解如何提高爬虫效率的方法,能够在学习scrapy框架的过程中更深入理解,有一种恍然大悟的感觉,整个学习过程是循序渐进的,感谢路飞学院的这次课程。

scrapy

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

  • 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

  • 先执行start_requests,返回的结果会转换成迭代器
  • 解析器
    • 将字符串转换成对象 xpath
    • 不加 标签对象
    • extract 列表
    • extract_first 第一个值
  • pipelines
    • 多个 数值小优先级高
    • 多个,返回值会传递给下一个pipelines的process_item
    • from scrapy.exceptions import DrapItem 丢弃 raise DrapItem()
    • 先判断是否有from_crawler
      • 有 obj = FilePipline.from_crawler()
      • 没有 obj = FilePipline()
      • 根据配置文件读取相关值,再进行pipeline处理
  • POST/请求头/cookie
  • 去重
    • url存数据库用hash
    • url不应该放数据库,应该放redis中(集合)
    • request_fingerprint 可以生产url唯一标识
    • dont_filter 默认False 去重

安装

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Linux
pip3 install scrapy
Windows
a. pip3 install wheel
b. 下载twisted http://www.lfd.uci.edu/~gohlke/pythonlibs/#twisted
c. 进入下载目录,执行 pip3 install Twisted‑17.1.0‑cp35‑cp35m‑win_amd64.whl
d. pip3 install scrapy
e. 下载并安装pywin32:https://sourceforge.net/projects/pywin32/files/

基本使用

基本命令

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scrapy startproject 项目名称
# 在当前目录中创建中创建一个项目文件(类似于Django)
scrapy genspider [-t template] <name> <domain>
# 创建爬虫应用
# 如:
scrapy gensipider -t basic oldboy oldboy.com
scrapy gensipider -t xmlfeed autohome autohome.com.cn
# PS:
查看所有命令:scrapy gensipider -l
查看模板命令:scrapy gensipider -d 模板名称
scrapy list
# 展示爬虫应用列表
scrapy crawl 爬虫应用名称
# 运行单独爬虫应用

项目结构以及爬虫应用简介

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project_name/
scrapy.cfg
project_name/
__init__.py
items.py
pipelines.py
settings.py
spiders/
__init__.py
爬虫1.py
爬虫2.py
爬虫3.py

文件说明:

  • scrapy.cfg 项目的主配置信息。(真正爬虫相关的配置信息在settings.py文件中)
  • items.py 设置数据存储模板,用于结构化数据,如:Django的Model
  • pipelines 数据处理行为,如:一般结构化的数据持久化
  • settings.py 配置文件,如:递归的层数、并发数,延迟下载等
  • spiders 爬虫目录,如:创建文件,编写爬虫规则

注意:一般创建爬虫文件时,以网站域名命名

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import scrapy
class IsmeSpider(scrapy.spiders.Spider):
# 爬虫名称
name = "isme"
# 允许的域名
allowed_domains = ["c.isme.pub"]
# 起始url
start_urls = [
"http://c.isme.pub",
]
def parse(self, response):
# 访问起始URL并获取结果后的回调函数
current_url = response.url
body = response.body
unicode_body = response.body_as_unicode()
# win下设置编码
import sys,os
sys.stdout=io.TextIOWrapper(sys.stdout.buffer,encoding='gb18030')

运行

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import scrapy
from scrapy.selector import HtmlXPathSelector
from scrapy.http.request import Request
class DigSpider(scrapy.Spider):
# 爬虫应用的名称,通过此名称启动爬虫命令
name = "dig"
# 允许的域名
allowed_domains = ["chouti.com"]
# 起始URL
start_urls = [
'http://dig.chouti.com/',
]
has_request_set = {}
def parse(self, response):
print(response.url)
hxs = HtmlXPathSelector(response)
page_list = hxs.select('//div[@id="dig_lcpage"]//a[re:test(@href, "/all/hot/recent/\d+")]/@href').extract()
for page in page_list:
page_url = 'http://dig.chouti.com%s' % page
key = self.md5(page_url)
if key in self.has_request_set:
pass
else:
self.has_request_set[key] = page_url
obj = Request(url=page_url, method='GET', callback=self.parse)
yield obj
@staticmethod
def md5(val):
import hashlib
ha = hashlib.md5()
ha.update(bytes(val, encoding='utf-8'))
key = ha.hexdigest()
return key

进入project_name目录,运行命令

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scrapy crawl spider_name --nolog

对于上述代码重要之处在于:

  • Request是一个封装用户请求的类,在回调函数中yield该对象表示继续访问
  • HtmlXpathSelector用于结构化HTML代码并提供选择器功能

选择器

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#!/usr/bin/env python
# -*- coding:utf-8 -*-
from scrapy.selector import Selector, HtmlXPathSelector
from scrapy.http import HtmlResponse
html = """<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title></title>
</head>
<body>
<ul>
<li class="item-"><a id='i1' href="link.html">first item</a></li>
<li class="item-0"><a id='i2' href="llink.html">first item</a></li>
<li class="item-1"><a href="llink2.html">second item<span>vv</span></a></li>
</ul>
<div><a href="llink2.html">second item</a></div>
</body>
</html>
"""
response = HtmlResponse(url='http://example.com', body=html,encoding='utf-8')
# hxs = HtmlXPathSelector(response)
# print(hxs)
# hxs = Selector(response=response).xpath('//a')
# print(hxs)
# hxs = Selector(response=response).xpath('//a[2]')
# print(hxs)
# hxs = Selector(response=response).xpath('//a[@id]')
# print(hxs)
# hxs = Selector(response=response).xpath('//a[@id="i1"]')
# print(hxs)
# hxs = Selector(response=response).xpath('//a[@href="link.html"][@id="i1"]')
# print(hxs)
# hxs = Selector(response=response).xpath('//a[contains(@href, "link")]')
# print(hxs)
# hxs = Selector(response=response).xpath('//a[starts-with(@href, "link")]')
# print(hxs)
# hxs = Selector(response=response).xpath('//a[re:test(@id, "i\d+")]')
# print(hxs)
# hxs = Selector(response=response).xpath('//a[re:test(@id, "i\d+")]/text()').extract()
# print(hxs)
# hxs = Selector(response=response).xpath('//a[re:test(@id, "i\d+")]/@href').extract()
# print(hxs)
# hxs = Selector(response=response).xpath('/html/body/ul/li/a/@href').extract()
# print(hxs)
# hxs = Selector(response=response).xpath('//body/ul/li/a/@href').extract_first()
# print(hxs)
# ul_list = Selector(response=response).xpath('//body/ul/li')
# for item in ul_list:
# v = item.xpath('./a/span')
# # 或
# # v = item.xpath('a/span')
# # 或
# # v = item.xpath('*/a/span')
# print(v)

注意:settings.py中设置DEPTH_LIMIT = 1来指定“递归”的层数。
更多选择器规则:http://scrapy-chs.readthedocs.io/zh_CN/latest/topics/selectors.html

格式化处理

上述实例只是简单的图片处理,所以在parse方法中直接处理。如果对于想要获取更多的数据,则可以利用Scrapy的items将数据格式化,然后统一交由pipelines来处理。

在items.py中创建类:

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# -*- coding: utf-8 -*-
import scrapy
class IsmeItem(scrapy.Item):
title = scrapy.Field()
href = scrapy.Field()

上述定义模板,以后对于从请求的源码中获取的数据同意按照此结构来获取,所以在spider中需要有一下操作:

spider

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from ..items import IsmeItem
class ChoutiSpider(scrapy.Spider):
name = 'chouti'
allowed_domains = ['chouti.com']
start_urls = ['http://dig.chouti.com/']
def parse(self, response):
"""
起始url下载完毕后,自动执行的回调函数,response封装了响应相关的所有内容
:param response:
:return:
"""
hxs = HtmlXPathSelector(response = response)
div_list = hxs.xpath("//div[@id='content-list']/div[@class='item']")
for div in div_list:
text = div.xpath(".//div[@class='part1']/a[1]/text()").extract_first().strip()
href = div.xpath(".//div[@class='part1']/a[1]/@href").extract_first()
itme = IsmeItem(title = text, href = href)
yield itme

此处代码的关键在于:

  • 将获取的数据封装在了Item对象中
  • yield Item对象 (一旦parse中执行yield Item对象,则自动将该对象交个pipelines的类来处理)

pipelines

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from scrapy.exceptions import DropItem
class CustomPipeline(object):
def __init__(self,v):
self.value = v
def process_item(self, item, spider):
print(item)
# 操作并进行持久化
# return表示会被后续的pipeline继续处理
return item
# 表示将item丢弃,不会被后续pipeline处理
# raise DropItem()
@classmethod
def from_crawler(cls, crawler):
"""
初始化时候,用于创建pipeline对象
:param crawler:
:return:
"""
val = crawler.settings.getint('MMMM')
return cls(val)
def open_spider(self,spider):
"""
爬虫开始执行时,调用
:param spider:
:return:
"""
print('000000')
def close_spider(self,spider):
"""
爬虫关闭时,被调用
:param spider:
:return:
"""
print('111111')

在settings.py中做如下配置:

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ITEM_PIPELINES = {
'isme.pipelines.IsmePipeline': 300,
}
# 每行后面的整型值,确定了他们运行的顺序,item按数字从低到高的顺序,通过pipeline,通常将这些数字定义在0-1000范围内。

递归的访问

以上的爬虫仅仅是爬去初始页,而我们爬虫是需要源源不断的执行下去,直到所有的网页被执行完毕

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# -*- coding: utf-8 -*-
import scrapy
from bs4 import BeautifulSoup
from scrapy.selector import HtmlXPathSelector
from scrapy.http import Request
from ..items import IsmeItem
class ChoutiSpider(scrapy.Spider):
name = 'chouti'
allowed_domains = ['chouti.com']
start_urls = ['https://dig.chouti.com/']
def parse(self, response):
"""
起始url下载完毕后,自动执行的回调函数,response封装了响应相关的所有内容
:param response:
:return:
"""
# print(response.text)
hxs = HtmlXPathSelector(response = response)
div_list = hxs.xpath("//div[@id='content-list']/div[@class='item']")
for div in div_list:
text = div.xpath(".//div[@class='part1']/a[1]/text()").extract_first().strip()
href = div.xpath(".//div[@class='part1']/a[1]/@href").extract_first()
itme = IsmeItem(title = text, href = href)
yield itme
pages = hxs.xpath("//div[@id='page-area']//a[@class='ct_pagepa']/@href").extract()
for page in pages:
page_url = "https://dig.chouti.com" + page
yield Request(url = page_url, callback=self.parse)

以上代码将符合规则的页面中的图片保存在指定目录,并且在HTML源码中找到所有的其他 a 标签的href属性,从而“递归”的执行下去,直到所有的页面都被访问过为止。以上代码之所以可以进行“递归”的访问相关URL,关键在于parse方法使用了 yield Request对象。

注:可以修改settings.py 中的配置文件,以此来指定“递归”的层数,如: DEPTH_LIMIT = 1

cookie

获取原始cookie以及解析后的cookie

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# 原始cookie
print(response.headers.getlist('Set-Cookie'))
# 解析之后的cookie
cookie_dict = {}
cookie_jar = CookieJar()
cookie_jar.extract_cookies(response, response.request)
for k, v in cookie_jar._cookies.items():
for i, j in v.items():
for m, n in j.items():
self.cookie_dict[m] = n.value
print(self.cookie_dict)

登录抽屉并点赞

手动操作cookie

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import scrapy
from scrapy.selector import HtmlXPathSelector
from scrapy.http import Request
from ..items import IsmeItem
from scrapy.http.cookies import CookieJar
class ChoutiSpider(scrapy.Spider):
name = 'chouti'
allowed_domains = ['chouti.com']
start_urls = ['https://dig.chouti.com/']
cookie_dict = {}
def parse(self, response):
"""
起始url下载完毕后,自动执行的回调函数,response封装了响应相关的所有内容
:param response:
:return:
"""
# print(response.text)
# print(response.url)
# print(response.request)
# print(response.headers)
# 原始cookie
print(response.headers.getlist('Set-Cookie'))
# 解析之后的cookie
cookie_dict = {}
cookie_jar = CookieJar()
cookie_jar.extract_cookies(response, response.request)
for k, v in cookie_jar._cookies.items():
for i, j in v.items():
for m, n in j.items():
self.cookie_dict[m] = n.value
print(self.cookie_dict)
req = Request(
url='https://dig.chouti.com/login',
method='POST',
headers={'Content-Type': 'application/x-www-form-urlencoded; charset=UTF-8'},
body='phone=8617600806797&password=6502570qq&oneMonth=1',
cookies=self.cookie_dict,
callback=self.parse_check_login
)
yield req
def parse_check_login(self, response):
print(response.text)
req = Request(
url='https://dig.chouti.com/link/vote?linksId=20719566',
method='POST',
cookies=self.cookie_dict,
callback=self.parse_check_result
)
yield req
def parse_check_result(self, response):
print(response.text)

自动处理cookies

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# -*- coding: utf-8 -*-
import scrapy
from scrapy.selector import HtmlXPathSelector
from scrapy.http import Request
from ..items import IsmeItem
from scrapy.http.cookies import CookieJar
class ChoutiSpider(scrapy.Spider):
name = 'chouti'
allowed_domains = ['chouti.com']
start_urls = ['https://dig.chouti.com/']
cookie_dict = {}
def start_requests(self):
for url in self.start_urls:
yield Request(url=url, callback=self.parse, meta={'cookiejar': True})
def parse(self, response):
"""
起始url下载完毕后,自动执行的回调函数,response封装了响应相关的所有内容
:param response:
:return:
"""
req = Request(
url='https://dig.chouti.com/login',
method='POST',
headers={'Content-Type': 'application/x-www-form-urlencoded; charset=UTF-8'},
body='phone=8617600806797&password=6502570qq&oneMonth=1',
meta={'cookiejar': True},
callback=self.parse_check_login
)
yield req
def parse_check_login(self, response):
print(response.text)
req = Request(
url='https://dig.chouti.com/link/vote?linksId=20719566',
method='POST',
meta={'cookiejar': True},
callback=self.parse_check_result
)
yield req
def parse_check_result(self, response):
print(response.text)

中间件

爬虫中间件

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class SpiderMiddleware(object):
def process_spider_input(self,response, spider):
"""
下载完成,parse函数执行之前执行,然后交给parse处理
:param response:
:param spider:
:return:
"""
pass
def process_spider_output(self,response, result, spider):
"""
spider处理完成,返回时调用 parse之后执行
:param response:
:param result:
:param spider:
:return: 必须返回包含 Request 或 Item 对象的可迭代对象(iterable)
"""
return result
def process_spider_exception(self,response, exception, spider):
"""
异常调用
:param response:
:param exception:
:param spider:
:return: None,继续交给后续中间件处理异常;含 Response 或 Item 的可迭代对象(iterable),交给调度器或pipeline
"""
return None
def process_start_requests(self,start_requests, spider):
"""
爬虫启动时调用 start_requests执行的时候触发
:param start_requests:
:param spider:
:return: 包含 Request 对象的可迭代对象
"""
return start_requests

下载中间件

  • 可以在请求前和请求之后定制一些功能
  • 所有请求头操作一些自定义的东西,如加个user-agent
  • 自动处理的cookies本质上也是使用的下载中间件
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class DownMiddleware1(object):
def process_request(self, request, spider):
"""
请求需要被下载时,经过所有下载器中间件的process_request调用
:param request:
:param spider:
:return:
None,继续后续中间件去下载;
Response对象,停止process_request的执行,开始执行process_response
Request对象,停止中间件的执行,将Request重新调度器
raise IgnoreRequest异常,停止process_request的执行,开始执行process_exception
"""
pass
def process_response(self, request, response, spider):
"""
spider处理完成,返回时调用
:param response:
:param result:
:param spider:
:return:
Response 对象:转交给其他中间件process_response
Request 对象:停止中间件,request会被重新调度下载
raise IgnoreRequest 异常:调用Request.errback
"""
print('response1')
return response
def process_exception(self, request, exception, spider):
"""
当下载处理器(download handler)或 process_request() (下载中间件)抛出异常
:param response:
:param exception:
:param spider:
:return:
None:继续交给后续中间件处理异常;
Response对象:停止后续process_exception方法
Request对象:停止中间件,request将会被重新调用下载
"""
return None

代理

代理,需要在环境变量中设置

方式一:使用默认,内置添加代理功能

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# 可以在start_requests里面加上
os.environ["http_proxy"] = "http://root:woshiniba@192.168.11.11:9999/"
os.environ["https_proxy"] = "http://192.168.11.11:9999/"

方式二:使用自定义下载中间件

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from scrapy.contrib.downloadermiddleware.httpproxy import HttpProxyMiddleware
import random, base64
import six
def to_bytes(text, encoding=None, errors='strict'):
if isinstance(text, bytes):
return text
if not isinstance(text, six.string_types):
raise TypeError('to_bytes must receive a unicode, str or bytes '
'object, got %s' % type(text).__name__)
if encoding is None:
encoding = 'utf-8'
return text.encode(encoding, errors)
class ProxyMiddleware(object):
def process_request(self, request, spider):
PROXIES = [
{'ip_port': '111.11.228.75:80', 'user_pass': ''},
{'ip_port': '120.198.243.22:80', 'user_pass': ''},
{'ip_port': '111.8.60.9:8123', 'user_pass': ''},
{'ip_port': '101.71.27.120:80', 'user_pass': ''},
{'ip_port': '122.96.59.104:80', 'user_pass': ''},
{'ip_port': '122.224.249.122:8088', 'user_pass': ''},
]
proxy = random.choice(PROXIES)
if proxy['user_pass'] is not None:
request.meta['proxy'] = to_bytes("http://%s" % proxy['ip_port'])
encoded_user_pass = base64.encodestring(to_bytes(proxy['user_pass']))
request.headers['Proxy-Authorization'] = to_bytes('Basic ' + encoded_user_pass)
else:
request.meta['proxy'] = to_bytes("http://%s" % proxy['ip_port'])
# settings
DOWNLOADER_MIDDLEWARES = {
'step8_king.middlewares.ProxyMiddleware': 500,
}

避免重复访问

scrapy默认使用 scrapy.dupefilter.RFPDupeFilter 进行去重,相关配置有:

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DUPEFILTER_CLASS = 'scrapy.dupefilter.RFPDupeFilter'
DUPEFILTER_DEBUG = False
JOBDIR = "保存范文记录的日志路径,如:/root/" # 最终路径为 /root/requests.seen

自定义URL去重操作

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from scrapy.dupefilter import BaseDupeFilter
from scrapy.utils.request import request_fingerprint
class MyDupeFilter(BaseDupeFilter):
def __init__(self):
self.visited_url = set()
@classmethod
def from_settings(cls, settings):
"""
初始化时,调用
:param settings:
:return:
"""
return cls()
def request_seen(self, request):
"""
检测当前请求是否已经被访问过
:param request:
:return: True表示已经访问过;False表示未访问过
"""
# 为请求创建唯一标识
ident = request_fingerprint(request)
if ident in self.visited_url:
return True
self.visited_url.add(ident)
return False
def open(self):
"""
开始爬去请求时,调用
:return:
"""
print('open replication')
def close(self, reason):
"""
结束爬虫爬取时,调用
:param reason:
:return:
"""
print('close replication')
def log(self, request, spider):
"""
记录日志
:param request:
:param spider:
:return:
"""
print('repeat', request.url)

自定义命令

  • 在spiders同级创建任意目录,如:commands
  • 在其中创建 crawlall.py 文件 (此处文件名就是自定义的命令)
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from scrapy.commands import ScrapyCommand
from scrapy.utils.project import get_project_settings
class Command(ScrapyCommand):
requires_project = True
def syntax(self):
return '[options]'
def short_desc(self):
return 'Runs all of the spiders'
def run(self, args, opts):
spider_list = self.crawler_process.spiders.list()
for name in spider_list:
self.crawler_process.crawl(name, **opts.__dict__)
self.crawler_process.start()
  • 在settings.py 中添加配置 COMMANDS_MODULE = ‘项目名称.目录名称’
  • 在项目目录执行命令:scrapy crawlall

单个爬虫

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import sys
from scrapy.cmdline import execute
if __name__ == '__main__':
execute(["scrapy","github","--nolog"])

自定义扩展

自定义扩展时,利用信号在指定位置注册指定操作

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from scrapy import signals
class MyExtension(object):
def __init__(self, value):
self.value = value
@classmethod
def from_crawler(cls, crawler):
val = crawler.settings.getint('MMMM')
ext = cls(val)
crawler.signals.connect(ext.spider_opened, signal=signals.spider_opened)
crawler.signals.connect(ext.spider_closed, signal=signals.spider_closed)
return ext
def spider_opened(self, spider):
print('open')
def spider_closed(self, spider):
print('close')

其他

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# -*- coding: utf-8 -*-
# Scrapy settings for step8_king project
#
# For simplicity, this file contains only settings considered important or
# commonly used. You can find more settings consulting the documentation:
#
# http://doc.scrapy.org/en/latest/topics/settings.html
# http://scrapy.readthedocs.org/en/latest/topics/downloader-middleware.html
# http://scrapy.readthedocs.org/en/latest/topics/spider-middleware.html
# 1. 爬虫名称
BOT_NAME = 'step8_king'
# 2. 爬虫应用路径
SPIDER_MODULES = ['step8_king.spiders']
NEWSPIDER_MODULE = 'step8_king.spiders'
# Crawl responsibly by identifying yourself (and your website) on the user-agent
# 3. 客户端 user-agent请求头
# USER_AGENT = 'step8_king (+http://www.yourdomain.com)'
# Obey robots.txt rules
# 4. 禁止爬虫配置 是否遵循爬虫协议
# True 把我爬虫名称发送到要爬取的网站,检测是否允许
# ROBOTSTXT_OBEY = False
# Configure maximum concurrent requests performed by Scrapy (default: 16)
# 5. 并发请求数
# CONCURRENT_REQUESTS = 4
# Configure a delay for requests for the same website (default: 0)
# See http://scrapy.readthedocs.org/en/latest/topics/settings.html#download-delay
# See also autothrottle settings and docs
# 6. 延迟下载秒数
# DOWNLOAD_DELAY = 2
# The download delay setting will honor only one of:
# 7. 单域名访问并发数,并且延迟下次秒数也应用在每个域名
# CONCURRENT_REQUESTS_PER_DOMAIN = 2
# 单IP访问并发数,如果有值则忽略:CONCURRENT_REQUESTS_PER_DOMAIN,并且延迟下次秒数也应用在每个IP
# CONCURRENT_REQUESTS_PER_IP = 3
# Disable cookies (enabled by default)
# 8. 是否支持cookie,cookiejar进行操作cookie
# COOKIES_ENABLED = True
# COOKIES_DEBUG = True
# Disable Telnet Console (enabled by default)
# 9. Telnet用于查看当前爬虫的信息,操作爬虫等...
# 使用telnet ip port ,然后通过命令操作
# TELNETCONSOLE_ENABLED = True
# TELNETCONSOLE_HOST = '127.0.0.1'
# TELNETCONSOLE_PORT = [6023,]
# 10. 默认请求头
# 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',
# }
# Configure item pipelines
# See http://scrapy.readthedocs.org/en/latest/topics/item-pipeline.html
# 11. 定义pipeline处理请求
# ITEM_PIPELINES = {
# 'step8_king.pipelines.JsonPipeline': 700,
# 'step8_king.pipelines.FilePipeline': 500,
# }
# 12. 自定义扩展,基于信号进行调用
# Enable or disable extensions
# See http://scrapy.readthedocs.org/en/latest/topics/extensions.html
# EXTENSIONS = {
# # 'step8_king.extensions.MyExtension': 500,
# }
# 13. 爬虫允许的最大深度,可以通过meta查看当前深度;0表示无深度
# DEPTH_LIMIT = 3
# 14. 爬取时,0表示深度优先Lifo(默认);1表示广度优先FiFo
# 后进先出,深度优先
# DEPTH_PRIORITY = 0
# SCHEDULER_DISK_QUEUE = 'scrapy.squeue.PickleLifoDiskQueue'
# SCHEDULER_MEMORY_QUEUE = 'scrapy.squeue.LifoMemoryQueue'
# 先进先出,广度优先
# DEPTH_PRIORITY = 1
# SCHEDULER_DISK_QUEUE = 'scrapy.squeue.PickleFifoDiskQueue'
# SCHEDULER_MEMORY_QUEUE = 'scrapy.squeue.FifoMemoryQueue'
# 15. 调度器队列
# SCHEDULER = 'scrapy.core.scheduler.Scheduler'
# from scrapy.core.scheduler import Scheduler
# 16. 访问URL去重
# DUPEFILTER_CLASS = 'step8_king.duplication.RepeatUrl'
# Enable and configure the AutoThrottle extension (disabled by default)
# See http://doc.scrapy.org/en/latest/topics/autothrottle.html
"""
17. 自动限速算法
from scrapy.contrib.throttle import AutoThrottle
自动限速设置
1. 获取最小延迟 DOWNLOAD_DELAY
2. 获取最大延迟 AUTOTHROTTLE_MAX_DELAY
3. 设置初始下载延迟 AUTOTHROTTLE_START_DELAY
4. 当请求下载完成后,获取其"连接"时间 latency,即:请求连接到接受到响应头之间的时间
5. 用于计算的... AUTOTHROTTLE_TARGET_CONCURRENCY
target_delay = latency / self.target_concurrency
new_delay = (slot.delay + target_delay) / 2.0 # 表示上一次的延迟时间
new_delay = max(target_delay, new_delay)
new_delay = min(max(self.mindelay, new_delay), self.maxdelay)
slot.delay = new_delay
"""
# 开始自动限速
# AUTOTHROTTLE_ENABLED = True
# The initial download delay
# 初始下载延迟
# AUTOTHROTTLE_START_DELAY = 5
# The maximum download delay to be set in case of high latencies
# 最大下载延迟
# AUTOTHROTTLE_MAX_DELAY = 10
# The average number of requests Scrapy should be sending in parallel to each remote server
# 平均每秒并发数
# AUTOTHROTTLE_TARGET_CONCURRENCY = 1.0
# Enable showing throttling stats for every response received:
# 是否显示
# AUTOTHROTTLE_DEBUG = True
# Enable and configure HTTP caching (disabled by default)
# See http://scrapy.readthedocs.org/en/latest/topics/downloader-middleware.html#httpcache-middleware-settings
"""
18. 启用缓存
目的用于将已经发送的请求或相应缓存下来,以便以后使用
from scrapy.downloadermiddlewares.httpcache import HttpCacheMiddleware
from scrapy.extensions.httpcache import DummyPolicy
from scrapy.extensions.httpcache import FilesystemCacheStorage
"""
# 是否启用缓存策略
# HTTPCACHE_ENABLED = True
# 缓存策略:所有请求均缓存,下次在请求直接访问原来的缓存即可
# HTTPCACHE_POLICY = "scrapy.extensions.httpcache.DummyPolicy"
# 缓存策略:根据Http响应头:Cache-Control、Last-Modified 等进行缓存的策略
# HTTPCACHE_POLICY = "scrapy.extensions.httpcache.RFC2616Policy"
# 缓存超时时间
# HTTPCACHE_EXPIRATION_SECS = 0
# 缓存保存路径
# HTTPCACHE_DIR = 'httpcache'
# 缓存忽略的Http状态码
# HTTPCACHE_IGNORE_HTTP_CODES = []
# 缓存存储的插件
# HTTPCACHE_STORAGE = 'scrapy.extensions.httpcache.FilesystemCacheStorage'
"""
19. 代理,需要在环境变量中设置
from scrapy.contrib.downloadermiddleware.httpproxy import HttpProxyMiddleware
方式一:使用默认
os.environ
{
http_proxy:http://root:woshiniba@192.168.11.11:9999/
https_proxy:http://192.168.11.11:9999/
}
方式二:使用自定义下载中间件
def to_bytes(text, encoding=None, errors='strict'):
if isinstance(text, bytes):
return text
if not isinstance(text, six.string_types):
raise TypeError('to_bytes must receive a unicode, str or bytes '
'object, got %s' % type(text).__name__)
if encoding is None:
encoding = 'utf-8'
return text.encode(encoding, errors)
class ProxyMiddleware(object):
def process_request(self, request, spider):
PROXIES = [
{'ip_port': '111.11.228.75:80', 'user_pass': ''},
{'ip_port': '120.198.243.22:80', 'user_pass': ''},
{'ip_port': '111.8.60.9:8123', 'user_pass': ''},
{'ip_port': '101.71.27.120:80', 'user_pass': ''},
{'ip_port': '122.96.59.104:80', 'user_pass': ''},
{'ip_port': '122.224.249.122:8088', 'user_pass': ''},
]
proxy = random.choice(PROXIES)
if proxy['user_pass'] is not None:
request.meta['proxy'] = to_bytes("http://%s" % proxy['ip_port'])
encoded_user_pass = base64.encodestring(to_bytes(proxy['user_pass']))
request.headers['Proxy-Authorization'] = to_bytes('Basic ' + encoded_user_pass)
print "**************ProxyMiddleware have pass************" + proxy['ip_port']
else:
print "**************ProxyMiddleware no pass************" + proxy['ip_port']
request.meta['proxy'] = to_bytes("http://%s" % proxy['ip_port'])
DOWNLOADER_MIDDLEWARES = {
'step8_king.middlewares.ProxyMiddleware': 500,
}
"""
"""
20. Https访问
Https访问时有两种情况:
1. 要爬取网站使用的可信任证书(默认支持)
DOWNLOADER_HTTPCLIENTFACTORY = "scrapy.core.downloader.webclient.ScrapyHTTPClientFactory"
DOWNLOADER_CLIENTCONTEXTFACTORY = "scrapy.core.downloader.contextfactory.ScrapyClientContextFactory"
2. 要爬取网站使用的自定义证书
DOWNLOADER_HTTPCLIENTFACTORY = "scrapy.core.downloader.webclient.ScrapyHTTPClientFactory"
DOWNLOADER_CLIENTCONTEXTFACTORY = "step8_king.https.MySSLFactory"
# https.py
from scrapy.core.downloader.contextfactory import ScrapyClientContextFactory
from twisted.internet.ssl import (optionsForClientTLS, CertificateOptions, PrivateCertificate)
class MySSLFactory(ScrapyClientContextFactory):
def getCertificateOptions(self):
from OpenSSL import crypto
v1 = crypto.load_privatekey(crypto.FILETYPE_PEM, open('/Users/wupeiqi/client.key.unsecure', mode='r').read())
v2 = crypto.load_certificate(crypto.FILETYPE_PEM, open('/Users/wupeiqi/client.pem', mode='r').read())
return CertificateOptions(
privateKey=v1, # pKey对象
certificate=v2, # X509对象
verify=False,
method=getattr(self, 'method', getattr(self, '_ssl_method', None))
)
其他:
相关类
scrapy.core.downloader.handlers.http.HttpDownloadHandler
scrapy.core.downloader.webclient.ScrapyHTTPClientFactory
scrapy.core.downloader.contextfactory.ScrapyClientContextFactory
相关配置
DOWNLOADER_HTTPCLIENTFACTORY
DOWNLOADER_CLIENTCONTEXTFACTORY
"""
"""
21. 爬虫中间件
class SpiderMiddleware(object):
def process_spider_input(self,response, spider):
'''
下载完成,执行,然后交给parse处理
:param response:
:param spider:
:return:
'''
pass
def process_spider_output(self,response, result, spider):
'''
spider处理完成,返回时调用
:param response:
:param result:
:param spider:
:return: 必须返回包含 Request 或 Item 对象的可迭代对象(iterable)
'''
return result
def process_spider_exception(self,response, exception, spider):
'''
异常调用
:param response:
:param exception:
:param spider:
:return: None,继续交给后续中间件处理异常;含 Response 或 Item 的可迭代对象(iterable),交给调度器或pipeline
'''
return None
def process_start_requests(self,start_requests, spider):
'''
爬虫启动时调用
:param start_requests:
:param spider:
:return: 包含 Request 对象的可迭代对象
'''
return start_requests
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.contrib.spidermiddleware.referer import RefererMiddleware
# Enable or disable spider middlewares
# See http://scrapy.readthedocs.org/en/latest/topics/spider-middleware.html
SPIDER_MIDDLEWARES = {
# 'step8_king.middlewares.SpiderMiddleware': 543,
}
"""
22. 下载中间件
class DownMiddleware1(object):
def process_request(self, request, spider):
'''
请求需要被下载时,经过所有下载器中间件的process_request调用
:param request:
:param spider:
:return:
None,继续后续中间件去下载;
Response对象,停止process_request的执行,开始执行process_response
Request对象,停止中间件的执行,将Request重新调度器
raise IgnoreRequest异常,停止process_request的执行,开始执行process_exception
'''
pass
def process_response(self, request, response, spider):
'''
spider处理完成,返回时调用
:param response:
:param result:
:param spider:
:return:
Response 对象:转交给其他中间件process_response
Request 对象:停止中间件,request会被重新调度下载
raise IgnoreRequest 异常:调用Request.errback
'''
print('response1')
return response
def process_exception(self, request, exception, spider):
'''
当下载处理器(download handler)或 process_request() (下载中间件)抛出异常
:param response:
:param exception:
:param spider:
:return:
None:继续交给后续中间件处理异常;
Response对象:停止后续process_exception方法
Request对象:停止中间件,request将会被重新调用下载
'''
return None
默认下载中间件
{
'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,
}
"""
# from scrapy.contrib.downloadermiddleware.httpauth import HttpAuthMiddleware
# Enable or disable downloader middlewares
# See http://scrapy.readthedocs.org/en/latest/topics/downloader-middleware.html
# DOWNLOADER_MIDDLEWARES = {
# 'step8_king.middlewares.DownMiddleware1': 100,
# 'step8_king.middlewares.DownMiddleware2': 500,
# }

更多请参见Scrapy文档:http://scrapy-chs.readthedocs.io/zh_CN/latest/index.html