Python: How do you decorate methods in child classes using a method in the parent class?

Question

code example:

class Parent:
    # something here that says that the function "foo" always starts in print("bar")

class Son(Parent):
    def foo(self):
        pass

class Daughter(Parent):
    def foo(self):
        print("q")


Son().foo() # prints "bar"
Daughter().foo() # prints "bar" then "q"

i tried to use @super.func though it's shoddy to copy paste that in every class that has Parent as the parent and has the foo method. any elegant solutions?

Answer 1

There may be more elegant methods, but you can decorate the methods of the subclasses in the __init_subclass__ hook

def bar_printer(f):
    def wrapper(*args, **kwargs):
        print('bar')
        return f(*args, **kwargs)

    return wrapper


class Parent:

    def foo(self):
        pass

    def __init_subclass__(cls, **kwargs):
        cls.foo = bar_printer(cls.foo)


class Son(Parent):
    def foo(self):
        pass


class Daughter(Parent):
    def foo(self):
        print("q")

son = Son()
daughter = Daughter()

son.foo()
daughter.foo()

Output:

bar
bar
q