July 2017
Intermediate to advanced
398 pages
11h 54m
Chinese
Content preview from Python数据处理
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高级网页抓取：屏幕抓取器与爬虫
｜
281
你可以同运行一个普通的抓取器一样，运行这个爬虫：
scrapy crawl package
你已经正式地完成了第一个爬虫！是否还有待完善的地方？有一个容易修复的
bug
遗留在
这段代码中了。你能找到它吗？如何修复它？［提示：查看你的
Python
版本，然后查看
返回版本的方式（即永远返回一个列表），与
grab_data
返回数据对比。］看看你是否能够
在爬虫脚本中修复这个问题。如果不能，可以参考本书仓库（
https://github.com/jackiekazil/
data-wrangling
），得到完整的修复后的代码。
Scrapy
是一个有效、快速、方便配置的工具。还有很多值得探索，你可以阅读该库的很棒
的文档（
http://doc.scrapy.org/en/latest/
）。配置你的脚本来使用数据库和特殊的信息抽取工
具，并且在自己的服务器上使用
Scrapyd
（
http://scrapyd.readthedocs.org/en/latest/
）运行它
们是很简单的。希望这是你之后众多
Scrapy
项目的第一个！
现在你理解了屏幕读取器、浏览器读取器和爬虫。让我们看看构建更加复杂的网页爬虫所
需要知道的其他一些事情。
12.3
网络
：
互联网的工作原理
，
以及为什么它会
让脚本崩溃
取决于运行抓取脚本的频率，以及每个脚本工作的重要性，你可能会碰到网络问题。是
的，互联网正在尝试破坏你的脚本。为什么？因为互联网认为如果你真的在乎，你会重
试。在网页抓取世界里丢失的连接、代理问题以及超时问题普遍存在 ...
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.