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@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@barrys-emacs.org> wrote:
On 2 Jul 2016, at 18:58, Guido van Rossum <gvanrossum@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__
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
they belong in the docs.
Agreed.
Barry
--Guido (mobile)
On Jul 2, 2016 10:32 AM, "Barry Scott" <barry@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
functions that 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
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-- --Guido van Rossum (python.org/~guido) _______________________________________________ Python-ideas mailing list Python-ideas@python.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/