July 2017
Intermediate to advanced
398 pages
11h 54m
Chinese
Content preview from Python数据处理
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251
第 12章
高级网页抓取：屏幕抓取器与爬虫
在第
11
章你已经开始培养网页抓取技能，学习了如何确定要抓取的内容，以及用什么方
式去哪里抓取。在这一章，我们会学习用更高级的抓取器来收集内容，比如基于浏览器的
抓取器和爬虫。
我们还会学习使用高级网页抓取工具调试常见问题，并介绍在抓取网页时会遇到的一些道
德问题。首先，我们会研究基于浏览器的网页抓取：通过
Python
直接使用浏览器从网页上
抓取内容。
12.1
基于浏览器的解析
有时，站点使用大量的
JavaScript
或其他页面加载后执行的代码来给页面填充内容。在这
些情况中，使用一个普通的网页抓取器来分析站点几乎是不可能的。你最后得到的是一个
空白的页面。如果你想要同页面进行交互（即，如果你需要点击按钮或者输入一些搜索文
本），也会碰到相同的问题。无论哪一种情况，你需要找出
屏幕阅读
（
screen read
）页面的
方法。屏幕读取器使用浏览器打开页面，在浏览器中加载页面之后读取并同它交互。
屏幕读取器很擅长执行通过一系列操作来获取信息才能完成的任务。出于这
个原因，屏幕读取器脚本也是自动化常规网页任务的简单方式。
在
Python
中最常用的屏幕读取库是
Selenium
（
http://selenium.googlecode.com/svn/trunk/
docs/api/py/index.html
）。
Selenium
是一个
Java
程序，用来打开浏览器，并且通过读取页
面同页面交互。如果你已经了解
Java
，可以使用
Java IDE
来与浏览器交互。我们会通过
Python ...
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