Is it bad form to call a classmethod as a method from an instance?
If you are tempted to call a class method from an instance you probably don't need a class method.
In the example you gave a static method would be more appropriate precisely because of your last remark (no self/cls interaction).
class C(object): @staticmethod def f(x): return x + xthis way it's "good form" to do both
c = C()c.f(2)and
C.f(2)
I don't recall using a classmethod like this from outside the class, but it is certainly ok for an instance method to call a classmethod on itself (e.g. self.foo() where foo is a classmethod). This makes sure that inheritance acts as expected, and will call .foo() in the right subclass instead of the base class.
It's mainly just confusing looking. If I were using your class and saw this, it would make me wonder what other surprises are in there, it just looks like bad design.
Is there a reason it's not just a staticmethod?