pyhon3 dynamically create methods from parent class

Question

Let's say I have a class defined like this:

classA():
    def do_one():
        print("one")
    def do_two():
        print("two")
    def some_other():
        print("other")

I want to create a derived class and automatically define every method from the parent class that starts with do

I tried this:

class B(A):
    pass

for m in dir(A):
    if m[0:3] == "do_":
        def dm(self):
            print("somebething before")
            getattr(super(),m)()
        dm.__name__ = m
        setattr(B,m,dm)

But i'm getting this error: RuntimeError: super(): __class__ cell not found Also is there a non-so-hacky/pytonic way of achieving this?

Answer 1

You cannot use super() without arguments outside a class definition. In order to perform lookups super() needs two arguments. Additionally, the definition of dm needs to be wrapped in another function. Otherwise, when it is executed the value of m will be taken from the global scope.

Putting this together, the following should work:

class A():
    def do_one(self):
        print("one")

    def do_two(self):
        print("two")

    def some_other(self):
        print("other")


class B(A):
    pass


for m in dir(B):
    if m[0:3] == "do_":

        def redef(m):
            def dm(self):
                print("something before")
                getattr(super(B, self), m)()

            return dm

        setattr(B, m, redef(m))

If you run:

x = B()
x.do_one()
x.do_two()
x.some_other()

It will give:

something before
one
something before
two
other