1. 안되는 Case

class Test:
    def print(self, name):
        def innerFnc(self, fncName):
            return fncName == name

        print("main function", name)
        return innerFnc

    

t = Test()
f = t.print("A")
main function A
type(f)
<class 'function'>
f("A")
Traceback (most recent call last):
  File "<pyshell#199>", line 1, in <module>
    f("A")
TypeError: Test.print.<locals>.innerFnc() missing 1 required positional argument: 'fncName'
f(t, "A")
True
f(t, "B")
False

Class function으로 인식한다.

2. 안되는 Case

class Test:
    def print(self, name):
        def innerFnc(self, fncName):
            return fncName == name

        print("main function", name)
        return innerFnc.__get__

    
t = Test()
f = t.print("A")
main function A
type(f)
<class 'method-wrapper'>
f("B")
<bound method Test.print.<locals>.innerFnc of 'B'>
f("B")("B")
False
f("B")("A")
True
f
<method-wrapper '__get__' of function object at 0x000002B45D215000>

3. 이렇게 해야 된다.

class Test:
    def print(self, name):
        def innerFnc(self, fncName):
            return fncName == name

        print("main function", name)
        return innerFnc.__get__(name)

    
t = Test()
f = t.print("A")
main function A
type(f)
<class 'method'>
f("B")
False
f("A")
True
f
<bound method Test.print.<locals>.innerFnc of 'A'>

Callable instance method를 return한다.