Is it bad form to call a classmethod as a method from an instance?

python class-method

Josh Gibson · Mar 28, 2009 · Viewed 21.6k times · Source

Ex.

If I have something like this:

class C(object):
    @classmethod
    def f(cls, x):
       return x + x

This will work:

c = C()

c.f(2)
4

But is that bad form? Should I only call

C.f()

c.__class__.f()

Obviously, this would only make sense in cases where f doesn't interact with self/cls expecting it to be class.

Answer

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 + x

this way it's "good form" to do both

c = C()
c.f(2)

and

C.f(2)