[Python-Dev] Semantics of __int__(), __index__()

Chris Angelico rosuav at gmail.com
Thu Apr 4 16:47:45 CEST 2013

On Fri, Apr 5, 2013 at 1:23 AM, Oscar Benjamin
<oscar.j.benjamin at 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:

class Bar(Foo):

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?


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