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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139
6.3 xpath を使った対象 HTML の設定
6.3
xpath
を使った対象
HTML
の設定
Scrapy
は、
xpath()
を使って対象
HTML
を設定します。
xpath
は、
X
（
HT
）
ML
ドキュメント
の各部分を定義する構文です。複雑になることもありますが基本は単純で、ほとんどの課題は解決
できます。
Chrome
の
Elements
タブを使ってソースの上にマウスポインタを乗せ、右クリックして［
Copy
Xpath
］を選ぶと、
HTML
要素の
xpath
が得られます。例えば、ノーベル賞ウィキリストの国名
の場合には（図
6-3
の
h2
）、
Argentina
（最初の国）の
xpath
を選ぶと以下が得られます。
//*[@id="mw-content-text"]/h2[1]
これは以下の
xpath
ルールを使って解読できます。
//E
ドキュメント内のどこかにある要素
<E>
（例えば、
//img
はページの全画像を取得する）。
//E[@id="foo"]
ID
が
foo
の要素
<E>
を選ぶ。
//*[@id="foo"]
ID
が
foo
の全要素を選ぶ。
//E/F[1]
要素
<E>
の最初の子要素
<F>
。
//E/*[1]
要素
<E>
の最初の子要素。
上記のルールに従うと、アルゼンチンのタイトル
//*[@id="mwcontent-text"]/h2[1]
は
ID
が
mw-content-text
の
DOM
要素の最初のヘッダ（
h2
）子要素です。これは以下の
HTML
に相当し
ます。
<div id="mw-content-text">
<h2> ...
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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.