September 2014
Intermediate to advanced
332 pages
6h 48m
Japanese
Content preview from Python文法詳解
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229
6.4 クラス
def __init__(self, ham, egg):
self.ham = ham
self.egg = egg
...
__slots__
を指定したクラスでは、インスタンスは
名前空間辞書
__dict__
を持たず、動的な
属性の追加ができません。上の例では、
Spam
クラスのインスタンスは、インスタンスの属性とし
て
ham
と
egg
だけを使用できます。他の属性値を追加すると、
AttributeError
例外が発生します。
6.4.7
メタプログラミング
次のようなクラス定義は、クラスオブジェクト
Spam
を作成します。
class Spam:
ham = 100
def egg(self, arg):
print(self, arg)
class
文を使わず、
type
オブジェクトを使っても、同様なクラスオブジェクトを作成できます。
def method(self, arg):
print(self, arg)
Spam = type('Spam', (), {'ham':100, 'egg':method})
type
オブジェクトは、整数型やクラスなど、全ての型オブジェクトの型となるオブジェクトで、
型オブジェクトを呼び出すとインスタンスが生成されるように、
type
オブジェクトを呼び出すと、
型オブジェクトが生成されます。このような、型オブジェクトの型となるオブジェクトを、メタク
ラスといいます。
class
文は、デフォルトでは
type
をメタクラスとしてクラスオブジェクトを作りますが、他の ...
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