August 2017
Intermediate to advanced
500 pages
12h 3m
Japanese
Content preview from PythonとJavaScriptではじめるデータビジュアライゼーション
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143
6.3 xpath を使った対象 HTML の設定
これで
xpath
をスクレイピング対象（受賞者の名前とリンクのテキスト）に設定したので、最
初の
Scrapy
スパイダーに
xpath
を組み込んでみましょう。
6.3.2
相対
xpath
を使った選択
上記のように、
Scrapy
の
xpath
での選択はセレクタのリストを返し、そのセレクタには独自の
xpath
メソッドがあります。
xpath
メソッドを使うときには、相対選択と絶対選択の違いをしっか
り理解するようにします。ノーベル賞ページの目次を例に使ってこの区別をはっきりさせておきま
しょう。
この目次は次のような構造になっています。
<div id='toc'... >
<ul ... >
<li ... >
<a href='Argentina'> ... </a>
</li>
...
</ul>
</div>
ノーベル賞ウィキページのこの目次はレスポンスに対する標準的な
xpath
クエリを使って選択で
き、
ID
が
toc
の
div
を取得します。
In [21]: toc = response.xpath('//div[@id="toc"]')[0]
すべての国の
<li>
リストタグを取得したければ、選択した
toc
div
に相対
xpath
を使用できま
す。以下の
2
つは同じで、どちらも現在の選択の子要素を相対的に選択します。
In [22]: lis = toc.xpath('.//ul/li')
In [23]: lis = toc.xpath('ul/li')
In [24]: ...
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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.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
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.