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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49
3
章
Python
における
データの読み書き
データ可視化の基本的なスキルとして、データを自在に移動できなければならないことがありま
す。データが
SQL
データベース、
CSV
（
Comma-Separated-Value
：カンマ区切り値）ファイル、
またはさらに難解な形式に含まれていても、容易にデータを読み込み、変換し、必要に応じてより
便利な形式で書き込めるのが理想でしょう。
Python
の大きな強みの
1
つは、このようなデータ操
作が簡単なことです。本章では、データ可視化ツールチェーンに必要なことは何かをよく理解して
もらうことに重点を置きます。
本章はチュートリアルとリファレンスの両方の性質を備え、後半では本章の各節を参照していま
す。
Python
データの読み書きの基本についての知識があれば、復習として本章の必要な部分だけ
を選んで読むのもよいでしょう。
3.1
ゆっくり行う
かなり昔に（
C
のような低水準言語を使って）プログラミングを始めたときにはデータ操作がと
てもやりにくかったものです。ファイルからの読み書きは、ボイラープレートコードや手作りのず
さんなコードなどを組み合わせた面倒なものでした。データベースからの読み込みも同じく困難
で、データのシリアライズ（直列化）については思い出したくないほどです。
Python
との出会い
は新しい世界でした。スピードについてはともかく、ファイルを開くのは非常に簡単でした。
file = open('data.txt')
その当時、
Python
はファイルからの読み書きを気持ちいいほど容易にし、洗練された文字列処 ...
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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.