Python: Why can't I use `super` on a class?

Question

Why can't I use super to get a method of a class's superclass?

Example:

Python 3.1.3 >>> class A(object): ... def my_method(self): pass >>> class B(A): ... def my_method(self): pass >>> super(B).my_method Traceback (most recent call last): File "<pyshell#2>", line 1, in <module> super(B).my_method AttributeError: 'super' object has no attribute 'my_method'

(Of course this is a trivial case where I could just do A.my_method, but I needed this for a case of diamond-inheritance.)

According to super's documentation, it seems like what I want should be possible. This is super's documentation: (Emphasis mine)

super() -> same as super(__class__, <first argument>)

super(type) -> unbound super object

super(type, obj) -> bound super object; requires isinstance(obj, type)

super(type, type2) -> bound super object; requires issubclass(type2, type)

[non-relevant examples redacted]

I deleted my answer - I got the same error. Very strange, will look into it a little more. — Jesse Vogt
– Jesse Vogt, Commented Jan 13, 2011 at 22:54

James · Accepted Answer · 2011-01-13 22:53:22Z

8

It looks as though you need an instance of B to pass in as the second argument.

http://www.artima.com/weblogs/viewpost.jsp?thread=236275

answered Jan 13, 2011 at 22:53

James

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1 Comment

ChristopheD Over a year ago

+1, Good read, part 2/3 of this article series describes the exact problems and real use case for unbound super objects: artima.com/weblogs/viewpost.jsp?thread=236278 (The secrets of unbound super objects)

Ram Rachum · Accepted Answer · 2011-01-13 23:11:51Z

6

According to this it seems like I just need to call super(B, B).my_method:

>>> super(B, B).my_method <function my_method at 0x00D51738> >>> super(B, B).my_method is A.my_method True

answered Jan 13, 2011 at 23:11

Ram Rachum

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3 Comments

James Over a year ago

Glad the linked source helped. :)

Glenn Maynard Over a year ago

Remember that this will give you unbound methods; the reason you normally need to say super(B, self) is to get a super object bound to an object, to retrieve bound methods.

ArtOfWarfare Over a year ago

... this looks really weird to me but works perfectly in Python 2.7.

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