Inconsistent results with super and __getattribute__ #39013

Activity

1. grodr commented on Aug 5, 2003

   

   grodrmannequin

   on Aug 5, 2003

   MannequinAuthor

   More actions

   Consider the following scenario of property overriding:

   >>> class Test(object):
   ... 	def __init__(self, n):
   ... 		self.__n = n
   ... 	#Properties.
   ... 	def __get_n(self):
   ... 		return self.__n
   ... 	def __set_n(self, n):
   ... 		self.__n = n
   ... 	n = property(__get_n, __set_n)
   ... 	
   >>> a = Test(42)
   >>> a.n
   42
   >>> a.n = 32
   >>> a.n
   32

   Now, let us override the n property:

   >>> class Test2(Test):
   ... 	def __init__(self, n):
   ... 		super(Test2, self).__init__(n)
   ... 	#Properties.
   ... 	def __get_n(self):
   ... 		return "got ya!"
   ... 	def __set_n(self, value):
   ... 		print "No way, jose!"
   ... 	n = property(__get_n, __set_n)
   ... 
   >>> a = Test2(42)
   >>> a.n
   'got ya!'
   >>> a.n = 0
   No way, jose!
   >>> a.n
   'got ya!'
   >>> super(Test2, a).n
   42

   So far so good, super is working well with properties. But
   now consider the following inconsistencies:

   >>> super(Test2, a).__getattribute__('n')
   'got ya!'
   >>> super(Test2, a).n
   42

   Also:

   >>> super(Test, Test2).__getattribute__('n')
   <property object at 0x01103300>
   >>> super(Test, Test2).__getattribute__('n').__get__(a)
   'got ya!'
   >>> super(Test, Test2).n
   Traceback (most recent call last):
     File "<interactive input>", line 1, in ?
   AttributeError: 'super' object has no attribute 'n'

   The last one is particularly damaging, because:

   >>> super(Test2, a).n = 32
   Traceback (most recent call last):
     File "<interactive input>", line 1, in ?
   AttributeError: 'super' object has no attribute 'n'

   I think the above should work, but whatever’s the
   answer, together with the super(Test, Test2) odd
   results it does make impossible using super and setting
   properties together.

   Tested with the latest Python 2.3 in win2k.

   With my best regards,
   G. Rodrigues

   P.S: bug 729913 talks of similar issues at the end: super
   does not seem to intercept special methods.
2. grodr

   added

   interpreter-core(Objects, Python, Grammar, and Parser dirs)(Objects, Python, Grammar, and Parser dirs)

   on Aug 5, 2003
3. devdanzin commented on Feb 13, 2009

   

   devdanzinmannequin

   on Feb 13, 2009

   Mannequin

   More actions

   Same behavior, is this a real issue?

   Current exception:
   TypeError: 'super' object has only read-only attributes (assign to .n)
4. devdanzin

   added

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on Feb 13, 2009
5. BreamoreBoy commented on Aug 18, 2010

   

   BreamoreBoymannequin

   on Aug 18, 2010

   Mannequin

   More actions

   Closed as no response to msg81870.
6. bitdancer

   closed this as completedon Feb 24, 2013
7. ezio-melotti

   transferred this issue fromon Apr 9, 2022