Using super in a subclass member in Python

Question

Consider the following code:

>>> class A:
...    k = 1
...
>>> class B(A):
...     k = super(B, cls).k
...
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "<console>", line 2, in B1
NameError: name 'B' is not defined

Why is this causing the error and what is the best way to get around it? Thanks.

Why are you trying to use super() in a class definition body in the first place? — Martijn Pieters
– Martijn Pieters, Commented May 15, 2014 at 21:29

Martijn Pieters · Accepted Answer · 2014-05-15 21:26:08Z

3

super() can only be used in a method, not in the class definition. It needs access to the class MRO, which is not yet known when the B class body is being built.

Even better, B isn't bound yet when the class is being defined! That doesn't happen until after the class body has been executed; you first need a class body before you can create a class object.

Just don't override k:

class A:
    k = 1

class B(A):
    pass

and B.k is inherited from A.

or reference it directly; you know exactly what base classes you have, when defining a class, after all:

class A:
    k = 1

class B(A):
    k = A.k

answered May 15, 2014 at 21:26

Martijn Pieters

1.1m326 gold badges4.2k silver badges3.4k bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Using super in a subclass member in Python

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related