August 2022
Intermediate to advanced
441 pages
11h 26m
Chinese
Content preview from Python文本分析
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104
｜
第
3
章
另一种避免内容提取的方法是混淆
HTML
代码，在这种代码中，
CSS
类的命名完全
随机。如果这些名称不会发生变化，则最初需要做更多工作来查找正确的选择器，
但此后可以自动工作。如果这些名称每天（或者每周等）都会变化，则内容提取将
变得非常困难。
3.19
总结和建议
网页抓取是一种强大且可扩展的技术，能够获取网页的内容。必要的
Python
基础架
构能够很好地支持抓取项目。
requests
库和
Beautiful Soup
的组合非常方便，并且适
合中等规模的抓取作业。
正如本章的介绍，我们可以系统地将大型抓取项目分为
URL
生成和下载两个阶段。
如果文档的数量非常大，则采用
wget
等外部工具可能比
requests
更合适。在下载完
所有内容后，就可以使用
Beautiful Soup
提取内容。
如果你想缩短等待的时间，则可以并行运行所有阶段。
无论在何种情况下，你都应该了解相关的法律规定，并遵守
robots.txt
中的规则，做
一名“有道德的爬虫”。
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