I created a classmethod and added it into a list in the class. How can i call it outside the class from the list?

Question

class ExFunc:

    @classmethod
    def exFunc(cls):
        print("exFunc has worked")
    
    func = exFunc
    funcs = [exFunc]


ExFunc.funcs[0]()

and i get TypeError: 'classmethod' object is not callable error in ExFunc.funcs0 line. I have some other functions in original code so i want to add them into a list and call them from list according to the input of the user. How can i do it?

I printed the ExFunc.funcs[0] code and it says its a classmethod and i tried to add () at its end because i thought i normally call functions when i put () at the end but it didnt work.

You can call it via descriptor `ExFunc.funcs[0].__get__(ExFunc)()` https://docs.python.org/3/howto/descriptor.html#simple-example-a-descriptor-that-returns-a-constant — Andrej Kesely, Jul 24 '23 at 20:40
Seen this? https://stackoverflow.com/questions/63567832/how-to-overcome-classmethod-is-not-callable-in-python — OneCricketeer, Jul 24 '23 at 20:40
There are other options here. Given that `exFunc` doesn't use its `cls` argument at all, there's an argument to be made that it should be a static method, or just a standalone function. You might also want `funcs` to store not the class method, but the underlying function (`exFunc.__func__`). — chepner, Jul 24 '23 at 20:42

S.B · Accepted Answer · 2023-07-24T21:28:05.070

classmethod objects are not callable, they "become" callable when you invoke them from either an instance of the class or the class itself. In that case Python turns them into a "method object" which has an object(the reference to the class) bound to it.

how is that possible? classmethods are descriptors.

You can mimic that magic I talked above, manually using the __get__ method. Note that you could pass an instance of that class as well.:

# simulating when it's called from the class
method = ExFunc.funcs[0].__get__(None, ExFunc)
method()

# simulating when it's called from an instance of the class
obj = ExFunc()
method = ExFunc.funcs[0].__get__(obj)
method()

There is however another solution, you can get the underlying function out of a classmethod object using __func__. Just note that it's a plain function with a parameter. You need to pass that:

ExFunc.funcs[0].__func__(ExFunc)

score 0 · Answer 2 · answered Jul 24 '23 at 20:45

A class method is associated with the class.

To call the class method you defined, you have to do ExFunc.exFunc().

If you want to call the method from a list, consider storing ExFunc in the list.

For more details, see: A better way to call Class Methods from List of Class Objects - Python

I created a classmethod and added it into a list in the class. How can i call it outside the class from the list?

2 Answers2