Michael Foord wrote:
On 15/04/2011 02:02, Greg Ewing wrote:
Michael Foord wrote:
What I was suggesting is that a method not calling super shouldn't
stop a *sibling* method being called, but could still prevent the
*parent* method being called.
There isn't necessarily a clear distinction between parents
and siblings.
class A:
...
class B(A):
...
class C(A, B):
...
In C, is A a parent of B or a sibling of B?
Its neither, as C can't exist:
class A: pass
...
class B(A): pass
...
class C(A,B):pass
...
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: Cannot create a consistent method resolution
order (MRO) for bases B, A
For a super call in C, B is a sibling to A. For a super call in B, A is
a parent.
With the semantics I was suggesting if C calls super, but A doesn't then
B would still get called.
A class cannot precede any of its sub-classes in an MRO,
see http://en.wikipedia.org/wiki/C3_linearization
If A is a "parent" (super-class) of B, then B must precede A in any MRO
that contains them both.
"Siblings", in the context of a single MRO are thus classes between
which there is no sub-class/super-class relation.
Mark.
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