classとself

目から鱗なお話。とりあえずメモ。

クラスとインスタンス

>>> class C:
...     def meth(self, arg):
...             self.val = arg
...             return self.val
... 
>>> arg = 9
>>> foo = C()
>>> foo.meth(arg)
9
>>> C.meth(foo, arg)
9
>>> foo.meth(arg) == C.meth(foo, arg)
True

myself

後からメソッド追加

>>> class C:
...     pass
... 
>>> def meth(myself, arg):
...     myself.val = arg
...     return myself.val
... 
>>> C.meth = meth
>>> 
>>> bar = C()
>>> bar.meth(arg)
9
>>> C.meth(bar, arg)
9
>>> bar.meth(arg) == C.meth(bar, arg)
True

参考リンク

• 和訳 なぜPythonのメソッド引数に明示的にselfと書くのか | TRIVIAL TECHNOLOGIES 4 @ats のイクメン日記
• Neopythonic: Why explicit self has to stay