July 2017
Intermediate to advanced
398 pages
11h 54m
Chinese
Content preview from Python数据处理
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232
｜
第
11
章
图 11-8：有很多页面的网络标签
你可以立即看到这个页面正在处理更多的请求。点击每一个请求，你可以看到每一个请求
加载的内容。请求顺序显示在网络标签中的时间线上。这可以帮助你理解如何抓取和处理
页面，来得到需要的内容。
通过点击每一个请求，可以看到初始页面加载后再加载大部分内容。点击初始页面的请
求，会发现并没有什么内容。我们想要问的第一个问题是：这里是否有一个
JavaScript
请
求或其他的请求使用
JSON
加载内容？如果有的话，对于我们的脚本来说，这可能是一个
恰当的“快捷方式”。
你知道如何解析和读取
JSON
（第
3
章），所以如果你在网络标签中找到一个
URL
，伴随着一个
JSON
响应，其中保存着你需要的数据，那么你可以使用
这个
URL
来获得数据，之后直接从响应中解析数据。你需要意识到所有可
能在请求中需要发送的头部（展示在网络标签中的头部小节），以得到正确
的响应。
如果这里没有简单的
JSON URL
匹配你需要的信息，或者信息散落在几个不同的的请求
中，需要人工整合它们到一起，那么可以确定，你需要使用一个基于浏览器的方法来抓取
站点。基于浏览器的网页抓取允许你读取看到的页面，而不仅是每一个请求。如果你需要
在正确抓取内容之前同一个下拉菜单交互，或执行一系列基于浏览器的操作，这可以很有
用。
网络标签帮助你找到包含所需内容的请求，以及是否有优秀的备选数据源。我们接下来会
查看
JavaScript
，看看这是否也会提供一些关于抓取器的想法。
11.2.3
控制台
：
同
JavaScript
交互
现在已经分析了页面的标记和结构 ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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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.