[Edu-sig] Consistency question
urnerk at qwest.net
Wed Sep 24 22:06:30 EDT 2003
So I'm wondering how one gets a handle on int-the-builtin-function versus
int the integer type (is there such?).
It would seem there'd be a builtin_function_or_method named int, in addition
to the int type, but I can't seem to get at it using dir() or type(). Is
there a way to bind the built-in int function to a name?
> -----Original Message-----
> From: edu-sig-bounces at python.org [mailto:edu-sig-bounces at python.org] On
> Behalf Of Guido van Rossum
> Sent: Wednesday, September 24, 2003 5:18 PM
> To: Kirby Urner
> Cc: edu-sig at python.org
> Subject: Re: [Edu-sig] Consistency question
> > My understanding is that int(5.0) actually triggers __int__ -- a method
> > inherited by all floats.
> > When I go dir(5.0), I see __int__ listed, and I can go:
> > >>> 5.0 .__int__()
> > 5
> > So far so good.
> > But then I can also go int('123') and get back 123. So why isn't
> __int__ a
> > method of string objects?
> > >>> '123' .__int__()
> > gets me an error, and dir('') doesn't show __int__ as being among
> > methods.
> > Why?
> > I'd like to clear up this confusion because I'm writing some tutorial
> > materials. What I don't understand, I can't rightly explain.
> int() special-cases various argument types. It only calls __int__
> when none of the special cases apply. An argument of type str is a
> special case (as is an argument of type unicode) because in that case,
> and *only* that case, the optional second 'base' argument is accepted.
> (If you really want to know more, RTSL. :-)
> --Guido van Rossum (home page: http://www.python.org/~guido/)
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