Am 04.04.2013 16:47, schrieb Chris Angelico: > On Fri, Apr 5, 2013 at 1:23 AM, Oscar Benjamin > <oscar.j.benja...@gmail.com> wrote: >> The reason for calling int(obj) is to get an object that is precisely >> of type int. When I call this I do not want any modified or additional >> methods or data attached to the resulting object. > > There's something I'm fundamentally not understanding about this > debate, and that is: How is it that calling a class can logically > return anything other than an instance of that class? Taking it to a > user-defined type: > > class Foo: > pass > > class Bar(Foo): > pass > > Is there any argument that I can pass to Foo() to get back a Bar()? > Would anyone expect there to be one? Sure, I could override __new__ to > do stupid things, but in terms of logical expectations, I'd expect > that Foo(x) will return a Foo object, not a Bar object. Why should int > be any different? What have I missed here?
I think the issue that the constructors for basic classes like int() are often seen as built-in functions that "cast" values to the respective type (or alternatively, functions that call the respective __method__ on the argument, like len()), not class constructors. FWIW, I agree with you that the "class constructor" view is the right one and would prefer exact int/str/... instances returned. Georg _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
