[Python-3000] __nonzero__ vs. __bool__

[tomer filiba]

patch updated (hopefully for the last time. it got me all bored :)


On 11/21/06, Brett Cannon <brett at python.org> wrote:
>
>
>
> On 11/21/06, Walter Dörwald <walter at livinglogic.de> wrote:
> >
> > tomer filiba wrote:
> > > patch updated
> >
> > You're fast! ;)
> >
> > AFAICT now we have the following problem: If
> > Objects/typeobject.c::slot_nb_bool() falls back to using __len__(), the
> > return value of __len__() must be a bool.
>
>
> Why can't the fallback usage just pass the return value from __len__ to
> bool() (forget the C function name) and return that result?  It's just like
> doing::
>
>   def bool(obj):
>       try:
>           return obj.__bool__()
>       except AttributeError:
>           return bool(len(obj))
>
> -Brett
>
> Servus,
> >    Walter
> >
> > > On 11/21/06, *Guido van Rossum* <guido at python.org
> > > <mailto:guido at python.org>> wrote:
> > >
> > >     I think it would set a good example if __bool__ was *required* to
> > >     return exactly True or False and no other object, not even int
> > >     instances equal to 0 or 1. Surely that can't be much of a burden.
> > Feel
> > >     free to upload an improved patch.
> > >
> > >     On 11/21/06, Walter Dörwald <walter at livinglogic.de
> > >     <mailto: walter at livinglogic.de>> wrote:
> > >     > Guido van Rossum wrote:
> > >     > > On 11/21/06, Ivan Krstić < krstic at solarsail.hcs.harvard.edu
> > >     <mailto:krstic at solarsail.hcs.harvard.edu>> wrote:
> > >     > >> Guido van Rossum wrote:
> > >     > >>> Can anyone help out evaluating this patch? If it has to wait
> >
> > >     for me
> > >     > >>> it's gonna be a looooooong wait...
> > >     > >> Looks fine to me functionally, although it seems to
> > >     gratuitously retab
> > >     > >> some code that used to be aligned with tabstop 8 to a tabstop
> > of 4.
> > >     > >
> > >     > > Thanks! I hope you meant "indentation level" instead of
> > "tabstop".
> > >     > > Tomer, can you fix the indentation to be whatever's prevailing
> > >     in the
> > >     > > file you're editing?
> > >     >
> > >     > Another question is whether __bool__() should be allowed to
> > return an
> > >     > int (or any other object), or if it *must* be a bool. (The patch
> >
> > >     > currently allows ints). What if __bool__() returns subclasses of
> > int,
> > >     > that overwrite __bool__() themself?
> > >     >
> > >     > Servus,
> > >     >    Walter
> > >     >
> > >     >
> > >
> > >
> > >     --
> > >     --Guido van Rossum (home page: http://www.python.org/~guido/<http://www.python.org/%7Eguido/>
> > )
> > >
> > >
> >
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> >
>
>
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