super problem

Uwe Mayer merkosh at hadiko.de
Sat Jun 25 07:49:51 EDT 2005


Hi,

I have a diamond-shaped multiple inheritanc chain with new style classes,
but super() does not call the parent class correctly:

-- snip --
from qtcanvas import *

class B2(QCanvasItem):
    def move(self, x,y):
        super(B2, self).move(0,0)
        print "B2"

class C2(QCanvasItem):
    def move(self, x,y):
        super(C2, self).move(0,0)
        print "C2"

class D2(QCanvasPolygonalItem, B2, C2):
    def move(self, x,y):
        super(D2, self).move(0,0)
        print "D2"

d2 = D2(None)
d2.move(0,0)
-- snip --
returns:

Traceback (most recent call last):
  File "tmp.py", line 46, in ?
    d2.move(0,0)
  File "tmp.py", line 42, in move
    super(D2, self).move(0,0)
  File "tmp.py", line 32, in move
    super(B2, self).move(0,0)
  File "tmp.py", line 37, in move
    super(C2, self).move(0,0)
AttributeError: 'super' object has no attribute 'move'

super(C2, self).move(0,0) should resolve to QCanvasItem.move
AFAIK super only works with new-style classes, so I checked:

>>> from qtcanvas import *
>>> isinstance(QCanvasItem, object)
True


A way to fix this is to introduce a dummy 

class A2(QCanvasItem):
    def move(self,x,y): QCanvasItem.move(self,x,y)

This is stupid, as it only delays execution by one intermediary call.


Is this a bug?

Thanks,
Ciao
Uwe     



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