On 14/04/2011 17:02, Raymond Hettinger wrote:
On Apr 14, 2011, at 8:34 AM, P.J. Eby wrote:
At 03:55 PM 4/14/2011 +0100, Michael Foord wrote:
Ricardo isn't suggesting that Python should always call super for you, but when
you *start* the chain by calling super then Python could ensure that all the
methods are called for you. If an individual method doesn't call super then a
theoretical implementation could skip the parents
methods (unless another child calls super).
That would break classes that deliberately don't call super. I can think of
examples in my own code that would break, especially in __init__() cases.
It's perfectly sensible and useful for there to be classes that intentionally fail to
call super(), and yet have a subclass that wants to use super(). So, this change would
expose an internal implementation detail of a class to its subclasses, and make
"fragile base class" problems worse. (i.e., where an internal change to a base
class breaks a previously-working subclass).
I agree. Better for someone to submit a recipe for a variant of super and see
if there is any uptake.
In Python 3 super is treated specially by the compiler, so an
alternative implementation that behaves similarly to the built-in one
modulo this change is not possible.
Two use cases for the suggested alternative behaviour have been
presented. What is the use case for a method not wanting to prevent its
*sibling* methods in a multiple inheritance situation being called?
I believe the use case Phillip (and others) have presented is for
methods preventing their *parent* methods being called.
All the best,
Michael Foord
Raymond
--
http://www.voidspace.org.uk/
May you do good and not evil
May you find forgiveness for yourself and forgive others
May you share freely, never taking more than you give.
-- the sqlite blessing http://www.sqlite.org/different.html
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