python：爬虫：Scrapy框架实例（详细步骤）

目标：

爬取以下网页内容，并存取到文件：

实现步骤：

产生步骤

步骤1：建立一个Scrapy工程

新建一个目录D:\pythontest\scrapy\pycodes，进入目录，然后执行命令 scrapy startproject python123demo

以上检测出并未安装 scrapy框架：


D:\pythontest\scrapy\pycodes>scrapy  startproject python123demo
New Scrapy project 'python123demo', using template directory 'd:\programdata\anaconda3\lib\site-packages\scrapy\templates\project', created in:
    D:\pythontest\scrapy\pycodes\python123demo

You can start your first spider with:
    cd python123demo
    scrapy genspider example example.com

D:\pythontest\scrapy\pycodes>

看到目录中生成了项目以及下面的文件：

下面逐一介绍目录文件以及其中包含子目录的作用：

步骤2：

在工程中产生一个Scrapy爬虫：

以下命令作用是生成一个 demo的 spider（爬虫）

D:\pythontest\scrapy\pycodes>cd python123demo

D:\pythontest\scrapy\pycodes\python123demo>scrapy genspider demo python123.io
Created spider 'demo' using template 'basic' in module:
  python123demo.spiders.demo

D:\pythontest\scrapy\pycodes\python123demo>

demo.py的内容：

因为我们的spider名字叫 demo，所以这个类也叫demo

# -*- coding: utf-8 -*-
import scrapy


class DemoSpider(scrapy.Spider):
    name = 'demo'
    allowed_domains = ['python123.io']  # python123.io 最开始提交给命令行的域名，指的是这个 爬虫在爬取网站的时候只能爬取这个域名以下的链接
    start_urls = ['http://python123.io/'] #列表形式包含了一个或多个url，就是scrapy框架所要爬取页面的初始页面
    #解析页面的方法（初始化时这里为空）
    def parse(self, response):
        pass


注意：parse()用于处理响应，解析内容形成字典 ，发现新的URL爬取请求。

步骤3：

配置产生的 spider爬虫，需修改demo.py文件

按照我们的要求访问我们的链接对相关内容进行爬取

我们对链接的解析部分，对于返回的HTML页面存成文件

需访问链接：

http://python123.io/ws/demo.html

然后更改爬取方法的具体功能，具体代码：

# -*- coding: utf-8 -*-
import scrapy


class DemoSpider(scrapy.Spider):
    name = 'demo'
    # allowed_domains = ['python123.io']  不需要 注释掉 
    start_urls = ['http://python123.io/ws/demo.html']

    def parse(self, response):
		fname = response.url.split('/')[-1] # 提取文件名保存为本地的文件名
		with open(fname,'wb') as f: # 返回的内容保存为文件
			f.write(response.body)
		self.log('Saved file %s.' % name)

步骤4：

运行爬虫获取网页

命令行中进入目录python123demo 执行命令：

scrapy crawl demo # 用crawl命令来执行demo这个爬虫

D:\pythontest\scrapy\pycodes\python123demo>scrapy crawl demo
2019-12-12 02:16:39 [scrapy.utils.log] INFO: Scrapy 1.8.0 started (bot: python123demo)
2019-12-12 02:16:39 [scrapy.utils.log] INFO: Versions: lxml 3.7.3.0, libxml2 2.9.4, cssselect 1.1.0, parsel 1.5.2, w3lib 1.21.0, Twisted 19.10.0, Python 3.6.1 |Anaconda 4.4.0 (64-bit)| (default, May 11 2017, 13:25:24) [MSC v.1900 64 bit (AMD64)], pyOpenSSL 17.0.0 (OpenSSL 1.1.1d  10 Sep 2019), cryptography 2.8, Platform Windows-10-10.0.17134-SP0
2019-12-12 02:16:39 [scrapy.crawler] INFO: Overridden settings: {'BOT_NAME': 'python123demo', 'NEWSPIDER_MODULE': 'python123demo.spiders', 'ROBOTSTXT_OBEY': True, 'SPIDER_MODULES': ['python123demo.spiders']}
2019-12-12 02:16:39 [scrapy.extensions.telnet] INFO: Telnet Password: 34478d1c14145d0f
2019-12-12 02:16:40 [scrapy.middleware] INFO: Enabled extensions:
['scrapy.extensions.corestats.CoreStats',
 'scrapy.extensions.telnet.TelnetConsole',
 'scrapy.extensions.logstats.LogStats']
2019-12-12 02:16:41 [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']
2019-12-12 02:16:41 [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']
2019-12-12 02:16:41 [scrapy.middleware] INFO: Enabled item pipelines:
[]
2019-12-12 02:16:41 [scrapy.core.engine] INFO: Spider opened
2019-12-12 02:16:41 [scrapy.extensions.logstats] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
2019-12-12 02:16:41 [scrapy.extensions.telnet] INFO: Telnet console listening on 127.0.0.1:6023
2019-12-12 02:16:41 [scrapy.downloadermiddlewares.redirect] DEBUG: Redirecting (301) to <GET https://python123.io/robots.txt> from <GET http://python123.io/robots.txt>
2019-12-12 02:16:41 [scrapy.core.engine] DEBUG: Crawled (404) <GET https://python123.io/robots.txt> (referer: None)
2019-12-12 02:16:41 [scrapy.downloadermiddlewares.redirect] DEBUG: Redirecting (301) to <GET https://python123.io/ws/demo.html> from <GET http://python123.io/ws/demo.html>
2019-12-12 02:16:41 [scrapy.core.engine] DEBUG: Crawled (200) <GET https://python123.io/ws/demo.html> (referer: None)
2019-12-12 02:16:41 [scrapy.core.engine] INFO: Closing spider (finished)
2019-12-12 02:16:41 [scrapy.statscollectors] INFO: Dumping Scrapy stats:
{'downloader/request_bytes': 888,
 'downloader/request_count': 4,
 'downloader/request_method_count/GET': 4,
 'downloader/response_bytes': 1901,
 'downloader/response_count': 4,
 'downloader/response_status_count/200': 1,
 'downloader/response_status_count/301': 2,
 'downloader/response_status_count/404': 1,
 'elapsed_time_seconds': 0.476027,
 'finish_reason': 'finished',
 'finish_time': datetime.datetime(2019, 12, 11, 18, 16, 41, 734011),
 'log_count/DEBUG': 4,
 'log_count/INFO': 10,
 'response_received_count': 2,
 'robotstxt/request_count': 1,
 'robotstxt/response_count': 1,
 'robotstxt/response_status_count/404': 1,
 'scheduler/dequeued': 2,
 'scheduler/dequeued/memory': 2,
 'scheduler/enqueued': 2,
 'scheduler/enqueued/memory': 2,
 'start_time': datetime.datetime(2019, 12, 11, 18, 16, 41, 257984)}
2019-12-12 02:16:41 [scrapy.core.engine] INFO: Spider closed (finished)

D:\pythontest\scrapy\pycodes\python123demo>

捕获页面存储在demo.html页面中：

HTML内容如下：

<html><head><title>This is a python demo page</title></head>
<body>
<p class="title"><b>The demo python introduces several python courses.</b></p>
<p class="course">Python is a wonderful general-purpose programming language. You can learn Python from novice to professional by tracking the following courses:
<a href="http://www.icourse163.org/course/BIT-268001" class="py1" id="link1">Basic Python</a> and <a href="http://www.icourse163.org/course/BIT-1001870001" class="py2" id="link2">Advanced Python</a>.</p>
</body></html>

代码分析：

实际上上面是简化版代码：

完整的demo.py

所有启动url通过列表形式。

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python：爬虫：Scrapy框架实例（详细步骤）

目标：

实现步骤：

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