September 2014
Intermediate to advanced
332 pages
6h 48m
Japanese
Content preview from Python文法詳解
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95
4.4 文字列型とバイト型
データは、数百万や数千万件となることも珍しくありません。タプルは固定長シーケンスなので、
リストよりもメモリの利用効率が良く、このような大量のデータを保持する場合には、リストでは
なくタプルを使えば、メモリ使用量の削減や、ガベージコレクションの負荷軽減などの効果が期待
できます。
4.4
文字列型とバイト型
Python
の文字列型は
Unicode
文字のシーケンスで、伝統的な
8bit
の文字からなる文字列型は
提供していません。
Unicode
ではないテキストは、文字ではなく画像などと同じバイナリデータ
として、
8bit
整数値のシーケンスであるバイト型で扱います。
テキストデータの入ったバイト型は、文字列型に変換できます。逆に、文字列型もバイト型のテ
キストデータに変換できます。バイト型から文字列型に変換することをデコード、逆に文字列型か
らバイト型に変換することを、エンコードといいます。
バイナリデータであるバイト型のデータを、文字列に変換するには、その変換ルールが必要に
なります。文字列データには様々な種類があり、日本のパーソナルコンピュータで広く使われる
ShiftJIS
、西ヨーロッパで使われる
latin1
、ロシア語で使われる
KOI8-R
など、国や言語、用途な
どによって、さまざまな形式のテキストデータが使われます。
Python
では、このようなバイト型のテキストデータと
Unicode
文字列を変換するルールを、エ
ンコーディングと呼び、エンコーディングに従って、バイト
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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.