On Thu, Apr 4, 2013 at 7:47 AM, Chris Angelico <ros...@gmail.com> wrote:
> 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? > A class can define a __new__ method that returns a different object. E.g. (python 3): >>> class C: ... def __new__(cls): return 42 ... >>> C() 42 >>> -- --Guido van Rossum (python.org/~guido)
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