Is it un-pythonic to define a function inside of a class method?

Question

PyLint told me that one of my class methods didn't need to be a method, but could just be a function in a class since it didn't use any class attribute. That made me do things I thought were "bad," but maybe they are Pythonic. Is the following code what Python wants us to do?

class TestClass(ParentClass):
    def __init__(self):
        def callbackfunction(text):
            print("hello")
        ParentClass.map_event_to_callback(ParentClass.event, callbackfunction)

where ParentClass.event emits text to its callback, but we'll just ignore that print "hello" instead. Even simpler:

class TestClass():
    def __init__(self, text):
        def printhello(text):
            print("hello")
        printhello(text)

assuming I don't care about text or printhello after __init__.

Answer 1

Creating a nested function for a callback is just fine. It even gives that function access to any locals in the parent function (as closures).

You can use a lambda if all you need to execute is one expression:

class TestClass(ParentClass):
    def __init__(self):
        ParentClass.map_event_to_callback(ParentClass.event, lambda text: print("hello"))