July 2018
Intermediate to advanced
596 pages
13h 35m
Japanese
Content preview from Pythonによるデータ分析入門 第2版 ―NumPy、pandasを使ったデータ処理
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70
3
章
Python
組み込みのデータ構造と関数、ファイルの扱い
3.1.4.3
ディクショナリで使えるキーの型
ディクショナリのバリューは、
Python
のどのようなオブジェクトでも使うことができますが、キー
ではスカラー値（
int
、
float
、
string
）のように変更不可能（
immutable
）なオブジェクトか、あるいは、
タプル（タプル内のすべてのオブジェクトも変更不可能）でなければなりません。技術的な言葉でいう
とハッシュ可能である必要があります。あるオブジェクトがハッシュ可能であるか（つまりディクショ
ナリのキーに使えるか）は、
hash
関数を使って調べることができます。
In [127]: hash('string')
Out[127]: 5023931463650008331
In [128]: hash((1, 2, (2, 3)))
Out[128]: 1097636502276347782
In [129]: hash((1, 2, [2, 3])) #
リストは変更可能（
mutable
）なので失敗する
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-129-800cd14ba8be> in <module>()
----> 1 hash((1, 2, [2, 3])) ...
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