October 2017
Intermediate to advanced
832 pages
13h 34m
Japanese
Content preview from Fluent Python ―Pythonicな思考とコーディング手法Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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13章演算子オーバーロードの適切な用法
演算子のオーバーロード（overload）については、背反した気持ちを抱いています。演算子のオーバーロードをできないようにしたのは、多くの人がC++で乱用しているのを見てきたからという、かなり個人的な理由によるものです。
——James GoslingJavaの設計者Herb Sutter：「The C Family of Languages: Interview with Dennis Ritchie, Bjarne Stroustrup, and James Gosling」より[13-01]
演算子をオーバーロードすれば、「+」や「|」のような中置演算子、あるいは「-」や「~」などの単項演算子をユーザ定義のオブジェクトから操作できます。関数呼び出しの()、属性アクセスの「.」、要素アクセスおよびスライスの[]もPythonでは演算子なのですが、ここでは単項演算子と中置演算子を説明します。
1.2.1節で、必要最小限の機能しかないVectorクラスで演算子を素朴に実装しました。例1-2では、特殊メソッドを使った演算子のオーバーロード方法を示すために__add__と__mul__メソッドを書きましたが、これらの実装には見落としやすい微妙な問題が含まれています。例9-2ではまた、Vector2d.__eq__メソッドがVector(3, 4) == [3, 4]をTrueとみなすといいましたが、この結果が意味をなすこともあれば、なさないこともあります。本章ではこうした問題に取り組みます。
本章では、次のことを説明します。
- 中置演算子のオペランドに異なる型が指定されたときのPythonの対処方法
- オペランドが各種の型に対応するための、ダックタイピングあるいは明示的な型検査の使い方 ...
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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.