Steven D'Aprano <st...@remove-this-cybersource.com.au> writes: > On Wed, 29 Sep 2010 02:20:55 +0100, MRAB wrote: > >> On 29/09/2010 01:19, Terry Reedy wrote: > >>> A person using instances of a class should seldom use special names >>> directly. They are, in a sense, implementation details, even if >>> documented. The idiom "if __name__ == '__main__':" is an exception. >>> >> __file__ is another exception. > > > As are __iter__, __next__, __add__, __dict__, and, yes, __class__, to > say nothing of all the other special methods.
I think by "person using instances of a class" Terry referred to the user of a class as opposed to the implementor. In that sense the user should be calling iter(foo) instead of foo.__iter__(), next(foo) instead of foo.__next__(), and foo+bar instead of foo.__add__(bar). Direct calls to special-name methods, such as __len__, often indicate that the programmer hasn't grasped how those methods are intended to be used in Python. Obviously, none of this applies to __dict__, __class__, and friends, nor does it apply to cases where you know what you're doing, such as invoking __<method>__ of a superclass. > (This may change in the future. Given type(), and isinstance(), I'm not > sure what value __class__ adds.) None whatsoever. __class__ used to be necessary to tell the appart instances of different old-style classes: >>> class X: pass # old-style ... >>> X().__class__ <class __main__.X at 0xb772f2fc> >>> type(X()) <type 'instance'> Now that classes produce real types, they are equivalent. -- http://mail.python.org/mailman/listinfo/python-list
