[Python-ideas] documentation for python3 super()

[Mark Daoust]

>You should be able to get more help by Googling for something like MRO.

Raymond's pycon2015 talk is also a good way to understand everything
involved.

https://www.youtube.com/watch?v=EiOglTERPEo




Mark Daoust

On Sat, Jul 2, 2016 at 3:28 PM, Guido van Rossum <gvanrossum at gmail.com>
wrote:

> The trick is in the mro. If you print Person.__mro__ you'll get a list
> showing that its MRO (method resolution order) is Person, QObject,
> Age, object. In Person, super() refers to QObject (the next class in
> the MRO). In QObject, *for a Person instance*, super() refers to Age.
> In Age, in this case, super() refers to object. The methods on object
> don't call super.
>
> Hope this helps -- you should be able to get more help by Googling for
> something like MRO.
>
> On Sat, Jul 2, 2016 at 11:45 AM, Barry Scott <barry at barrys-emacs.org>
> wrote:
> >
> > On 2 Jul 2016, at 18:58, Guido van Rossum <gvanrossum at gmail.com> wrote:
> >
> > No, super() does not (directly) call multiple functions. The function it
> > calls has to call the next with another super() call. Also, __init__() is
> > not special, nor is **kwds
> >
> >
> > The thing I do not understand is why did super() call 2 __init__
> functions
> > given the code I attached?
> > The one in QObject and the one in Age.
> >
> > This is the output I get with python 3.5:
> >
> > $ python3.5 super_example.py
> > instance of Person.__init__
> > instance of QObject.__init__
> > instance of Age.__init__
> > Person.describe()
> > name: Barry
> > QObject.describe()
> >
> > I see no obvious code that should call Age.__init__, which is why I
> > concluded that there is something about super() that is not documented.
> >
> > super() itself is special, it knows the class and instance.
> >
> > There are conventions around all of this though. It may be worth
> documenting
> > those, as long as it is made clear which part of the docs is about
> > conventions (as opposed to how things work).
> >
> > There are also opinions about those conventions. Here I am not so sure
> that
> > they belong in the docs.
> >
> > Agreed.
> >
> > Barry
> >
> > --Guido (mobile)
> >
> > On Jul 2, 2016 10:32 AM, "Barry Scott" <barry at barrys-emacs.org> wrote:
> >>
> >> I have read the python3.5 docs for super() and
> >> https://rhettinger.wordpress.com/2011/05/26/super-considered-super/.
> >>
> >> Between the two sources I still have no clear idea of what super() will
> >> do and why it will doe what it does.
> >>
> >> I hope to get feedback that can be used as the basis to update the
> python
> >> docs.
> >>
> >> For single inheritance the use of super() does not seem to have any
> >> surprises.
> >>
> >> But in the case of a class with multiple-inheritance more then 1
> function
> >> may be called by 1 call to super().
> >>
> >> What are the rules for which functions are called by super() in the
> >> multiple
> >> inheritance case?
> >>
> >> Is __init__ special or can other super() calls end up
> >> calling more then 1 function?
> >>
> >> What is the role of **kwds with super()?
> >>
> >> Here is the code I used to show the __init__ multiple calls.
> >>
> >> The attached example shows that one call to super() causes 2 to
> >> __init__ of bases of Person. But describe does not follow the pattern
> >> Age.describe is not called.
> >>
> >> Barry
> >>
> >> _______________________________________________
> >> Python-ideas mailing list
> >> Python-ideas at python.org
> >> https://mail.python.org/mailman/listinfo/python-ideas
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> >
> >
>
>
>
> --
> --Guido van Rossum (python.org/~guido)
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