快速上手——我用scrapy写爬虫（一）

写在前面

用python写爬虫的人很多，python的爬虫框架也很多，诸如pyspider 和 scrapy，笔者还是笔记倾向于scrapy，本文就用python写一个小爬虫demo。
本文适用于有一定python基础的，并且对爬虫有一定了解的开发者。

安装 Scrapy

检查环境，python的版本为3.6.2，pip为9.0.1

F:\techlee\python>python --version
Python 3.6.2

F:\techlee\python>pip --version
pip 9.0.1 from d:\program files\python\python36-32\lib\site-packages (python 3.6)

安装scrapy框架

F:\techlee\python>pip install scrapy
Collecting scrapy
  Downloading Scrapy-1.4.0-py2.py3-none-any.whl (248kB)
    100% |████████████████████████████████| 256kB 188kB/s
    // 漫长的安装过程
Successfully installed Twisted-17.9.0 scrapy-1.4.0

如果报错：

error: Microsoft Visual C++ 14.0 is required. Get it with "Microsoft Visual C++ Build Tools": http://landinghub.visualstudio.com/visual-cpp-build-tools

请安装Visual C++ 2015 Build Tools
http://landinghub.visualstudi...

安装完成

F:\techlee\python>scrapy version
Scrapy 1.4.0

创建项目

F:\techlee\python>scrapy startproject scrapyDemo
New Scrapy project 'scrapyDemo', using template directory 'd:\\program files\\python\\python36-32\\lib\\site-packages\\scrapy\\templates\\project', created in:
    F:\techlee\python\scrapyDemo

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

目录结构

scrapyDemo/
    scrapy.cfg            # 部署配置文件

    scrapyDemo/           # python模块
        __init__.py

        items.py          # 数据容器

        pipelines.py      # project pipelines file

        settings.py       # 配置文件

        spiders/          # Spider类定义了如何爬取某个(或某些)网站
            __init__.py

创建执行爬取的类ImoocSpider在 scrapyDemo/spiders中

# -*- coding: utf-8 -*-
import scrapy
from urllib import parse as urlparse

# 慕课网爬取
class ImoocSpider(scrapy.Spider):
    # spider的名字定义了Scrapy如何定位(并初始化)spider，所以其必须是唯一的
    name = "imooc"

    # URL列表
    start_urls = ['http://www.imooc.com/course/list']
    #  域名不在列表中的URL不会被爬取。
    allowed_domains = ['www.imooc.com']

    def parse(self, response):        
        learn_nodes = response.css('a.course-card')
        for learn_node in learn_nodes :
            learn_url = learn_node.css("::attr(href)").extract_first()
            yield scrapy.Request(url=urlparse.urljoin(response.url,learn_url),callback=self.parse_learn)
        
    def parse_learn(self, response):
        title = response.xpath('//h2[@class="l"]/text()').extract_first()
        content = response.xpath('//div[@class="course-brief"]/p/text()').extract_first()
        url = response.url
        print ('标题：' + title)
        print ('地址：' + url)

开始爬取

F:\techlee\python\scrapyDemo>scrapy crawl imooc

如果出现，则缺少win32api库，选择相应的版本

下载地址：https://sourceforge.net/proje...

import win32api
ModuleNotFoundError: No module named 'win32api'

大功告成

看到如下输出，就说明爬取成功啦

F:\techlee\python\scrapyDemo>scrapy crawl imooc
2017-10-17 14:28:32 [scrapy.utils.log] INFO: Scrapy 1.4.0 started (bot: scrapyDemo)
……
2017-10-17 14:28:32 [scrapy.core.engine] INFO: Spider opened
2017-10-17 14:28:32 [scrapy.extensions.logstats] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
2017-10-17 14:28:32 [scrapy.extensions.telnet] DEBUG: Telnet console listening on 127.0.0.1:6023
2017-10-17 14:28:32 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://www.imooc.com/robots.txt> (referer: None)
2017-10-17 14:28:33 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://www.imooc.com/course/list> (referer: None)
2017-10-17 14:28:33 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://www.imooc.com/learn/876> (referer: http://www.imooc.com/course/list)
标题：集成MultiDex项目实战
地址：http://www.imooc.com/learn/876
2017-10-17 14:28:33 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://www.imooc.com/learn/893> (referer: http://www.imooc.com/course/list)
标题：阿里D2前端技术论坛——2016初心
地址：http://www.imooc.com/learn/893
2017-10-17 14:28:33 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://www.imooc.com/learn/890> (referer: http://www.imooc.com/course/list)
2017-10-17 14:28:33 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://www.imooc.com/learn/888> (referer: http://www.imooc.com/course/list)
标题：Hadoop进阶
地址：http://www.imooc.com/learn/890
标题：Javascript实现二叉树算法
地址：http://www.imooc.com/learn/888
2017-10-17 14:28:33 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://www.imooc.com/learn/894> (referer: http://www.imooc.com/course/list)
标题：Fragment应用上
地址：http://www.imooc.com/learn/894
2017-10-17 14:28:34 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://www.imooc.com/learn/887> (referer: http://www.imooc.com/course/list)
标题：PHP-面向对象
地址：http://www.imooc.com/learn/887
2017-10-17 14:28:34 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://www.imooc.com/learn/900> (referer: http://www.imooc.com/course/list)
2017-10-17 14:28:34 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://www.imooc.com/learn/889> (referer: http://www.imooc.com/course/list)
2017-10-17 14:28:34 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://www.imooc.com/learn/901> (referer: http://www.imooc.com/course/list)
标题：Sketch的基础实例应用
地址：http://www.imooc.com/learn/900
标题：ElasticSearch入门
地址：http://www.imooc.com/learn/889
标题：使用Google Guice实现依赖注入
地址：http://www.imooc.com/learn/901
2017-10-17 14:28:34 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://www.imooc.com/learn/867> (referer: http://www.imooc.com/course/list)
标题：Docker入门
地址：http://www.imooc.com/learn/867
2017-10-17 14:28:34 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://www.imooc.com/learn/878> (referer: http://www.imooc.com/course/list)
标题：Android图表绘制之直方图
地址：http://www.imooc.com/learn/878
2017-10-17 14:28:34 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://www.imooc.com/learn/892> (referer: http://www.imooc.com/course/list)
标题：UI版式设计
地址：http://www.imooc.com/learn/892
2017-10-17 14:28:35 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://www.imooc.com/learn/877> (referer: http://www.imooc.com/course/list)
2017-10-17 14:28:35 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://www.imooc.com/learn/886> (referer: http://www.imooc.com/course/list)
标题：RxJava与RxAndroid基础入门
地址：http://www.imooc.com/learn/877
标题：iOS开发之Audio特辑
地址：http://www.imooc.com/learn/886
2017-10-17 14:28:35 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://www.imooc.com/learn/861> (referer: http://www.imooc.com/course/list)
标题：基于Websocket的火拼俄罗斯（基础）
地址：http://www.imooc.com/learn/861
2017-10-17 14:28:35 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://www.imooc.com/learn/895> (referer: http://www.imooc.com/course/list)
2017-10-17 14:28:35 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://www.imooc.com/learn/882> (referer: http://www.imooc.com/course/list)
标题：2017AWS 技术峰会——大数据技术专场
地址：http://www.imooc.com/learn/895
标题：基于websocket的火拼俄罗斯（单机版）
地址：http://www.imooc.com/learn/882

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