scrapy 蜘蛛 选择器 存储URL数据

概述

在上一篇中,大致介绍了scripy的基础知识,下面介绍scrapy蜘蛛

蜘蛛经历周期

1. 初始化请求,指定从这些请求中下载页面,并触发回调函数.
2. 在回调函数中,继续解析请求的网页,从中提取结构化数据.
3. 其中在回调函数中,可以从中提取页面内容.
4. 持久化保存

scrapy.Spider

每个蜘蛛必须继承的该类,该类为所有蜘蛛的父类

该类提供了一个默认的start_requests()的实现.

若要定义一个蜘蛛,必须在构造方法中继承该类

一个蜘蛛的例子

import scrapy


class QuotesSpider(scrapy.Spider):
    # 识别蜘蛛
    name = "quotes"

    # 定义需要爬去的请求
    def start_requests(self):
        urls = [
            'http://quotes.toscrape.com/page/1/',
            'http://quotes.toscrape.com/page/2/',
        ]
        for url in urls:
            yield scrapy.Request(url = url, callback=self.parse)


    # 定义调用方法
    def parse(self, response):
        for quote in response.css('div.quote'):
            # 迭代列表
            yield {
                'text': quote.css('span.text::text').get(),
                'author': quote.css('small.author::text').get(),
                'tags': quote.css('div.tags a.tag::text').getall(),
            }

选择器

首先打开shell

(venv) ➜  tutorial scrapy shell https://docs.scrapy.org/en/latest/_static/selectors-sample1.html
2019-04-03 22:49:56 [scrapy.utils.log] INFO: Scrapy 1.6.0 started (bot: tutorial)
2019-04-03 22:49:56 [scrapy.utils.log] INFO: Versions: lxml 4.3.3.0, libxml2 2.9.9, cssselect 1.0.3, parsel 1.5.1, w3lib 1.20.0, Twisted 18.9.0, Python 3.6.7 (default, Oct 22 2018, 11:32:17) - [GCC 8.2.0], pyOpenSSL 19.0.0 (OpenSSL 1.1.1b  26 Feb 2019), cryptography 2.6.1, Platform Linux-4.18.0-17-generic-x86_64-with-Ubuntu-18.10-cosmic
2019-04-03 22:49:56 [scrapy.crawler] INFO: Overridden settings: {'BOT_NAME': 'tutorial', 'DUPEFILTER_CLASS': 'scrapy.dupefilters.BaseDupeFilter', 'LOGSTATS_INTERVAL': 0, 'NEWSPIDER_MODULE': 'tutorial.spiders', 'ROBOTSTXT_OBEY': True, 'SPIDER_MODULES': ['tutorial.spiders']}
2019-04-03 22:49:56 [scrapy.extensions.telnet] INFO: Telnet Password: 7f8ee92d3d9ad6cc
2019-04-03 22:49:56 [scrapy.middleware] INFO: Enabled extensions:
['scrapy.extensions.corestats.CoreStats',
 'scrapy.extensions.telnet.TelnetConsole',
 'scrapy.extensions.memusage.MemoryUsage']
2019-04-03 22:49:56 [scrapy.middleware] INFO: Enabled downloader middlewares:
['scrapy.downloadermiddlewares.robotstxt.RobotsTxtMiddleware',
 'scrapy.downloadermiddlewares.httpauth.HttpAuthMiddleware',
 'scrapy.downloadermiddlewares.downloadtimeout.DownloadTimeoutMiddleware',
 'scrapy.downloadermiddlewares.defaultheaders.DefaultHeadersMiddleware',
 'scrapy.downloadermiddlewares.useragent.UserAgentMiddleware',
 'scrapy.downloadermiddlewares.retry.RetryMiddleware',
 'scrapy.downloadermiddlewares.redirect.MetaRefreshMiddleware',
 'scrapy.downloadermiddlewares.httpcompression.HttpCompressionMiddleware',
 'scrapy.downloadermiddlewares.redirect.RedirectMiddleware',
 'scrapy.downloadermiddlewares.cookies.CookiesMiddleware',
 'scrapy.downloadermiddlewares.httpproxy.HttpProxyMiddleware',
 'scrapy.downloadermiddlewares.stats.DownloaderStats']
2019-04-03 22:49:56 [scrapy.middleware] INFO: Enabled spider middlewares:
['scrapy.spidermiddlewares.httperror.HttpErrorMiddleware',
 'scrapy.spidermiddlewares.offsite.OffsiteMiddleware',
 'scrapy.spidermiddlewares.referer.RefererMiddleware',
 'scrapy.spidermiddlewares.urllength.UrlLengthMiddleware',
 'scrapy.spidermiddlewares.depth.DepthMiddleware']
2019-04-03 22:49:56 [scrapy.middleware] INFO: Enabled item pipelines:
[]
2019-04-03 22:49:56 [scrapy.extensions.telnet] INFO: Telnet console listening on 127.0.0.1:6023
2019-04-03 22:49:56 [scrapy.core.engine] INFO: Spider opened
2019-04-03 22:49:58 [scrapy.core.engine] DEBUG: Crawled (200) <GET https://docs.scrapy.org/robots.txt> (referer: None)
2019-04-03 22:49:59 [scrapy.core.engine] DEBUG: Crawled (200) <GET https://docs.scrapy.org/en/latest/_static/selectors-sample1.html> (referer: None)
[s] Available Scrapy objects:
[s]   scrapy     scrapy module (contains scrapy.Request, scrapy.Selector, etc)
[s]   crawler    <scrapy.crawler.Crawler object at 0x7fda92a1f908>
[s]   item       {}
[s]   request    <GET https://docs.scrapy.org/en/latest/_static/selectors-sample1.html>
[s]   response   <200 https://docs.scrapy.org/en/latest/_static/selectors-sample1.html>
[s]   settings   <scrapy.settings.Settings object at 0x7fda915606d8>
[s]   spider     <DefaultSpider 'default' at 0x7fda91269080>
[s] Useful shortcuts:
[s]   fetch(url[, redirect=True]) Fetch URL and update local objects (by default, redirects are followed)
[s]   fetch(req)                  Fetch a scrapy.Request and update local objects 
[s]   shelp()           Shell help (print this help)
[s]   view(response)    View response in a browser
>>>

在 shell 加载以后,将会response作为响应变量.

并在response.selector属性中附加选择器.

>>> response.xpath('//title/text()')
[<Selector xpath='//title/text()' data='Example website'>]
>>>

实际提取文本数据使用get

>>> response.xpath('//title/text()').get()
'Example website'
>>>

css选择器也可

>>> response.css('title::text').get()
'Example website'
>>>

剩下的大概也没啥了.下面干啥呢.开爬,随便爬爬得了..学不了那么深...