[Tutor] use of __new__

[spir]

Le Fri, 12 Jun 2009 09:05:35 -0400,
Kent Johnson <kent37 at tds.net> s'exprima ainsi:

> On Fri, Jun 12, 2009 at 8:37 AM, Lie Ryan<lie.1296 at gmail.com> wrote:
> >>>> class Normal(object):
> > ...     def __new__(cls, arg):
> > ...         if arg:
> > ...             return Special(arg)
> > ...         else:
> > ...             ret = super(Normal, cls).__new__(cls)
> > ...             ret.__init__(arg)
> > ...             return ret
> 
> I think the else case should be
>   ret = super(Normal, cls).__new__(cls, arg)
>   return ret
> 
> i.e. pass the same args to super.__new__() and don't explicitly call
> __init__().
> 
> Kent
 
Holà, Kent,

Don't you have a comment in the 'if' case, too? Namely that __init__ is not invoked explicitely, while the docs clearly state:

<< f __new__() returns an instance of cls, then the new instance’s __init__() method will be invoked like __init__(self[, ...]), where self is the new instance and the remaining arguments are the same as were passed to __new__().

If __new__() does not return an instance of cls, then the new instance’s __init__() method will not be invoked.>>

Denis
------
la vita e estrany