how to define deep copy of subclass if super class has customized deep copy

Question

My super class A has a method copy(), which is a customized deep copy function. The sub class B wants to inherit this deep-copy function while also deep-copying its own member and methods.

In the following explaining example, the copy function only copies the "A part" of B. My question is how can I modify the copy function in order to also deep-copy the member T and method addOn() and other potential class features?

class B(A):
    def __init__(self, T):
        super().__init__()
        self.T = T
    def addOn(self):
        print("additional feature")
    def copy(self):
        return super().copy()

Answer 1

You've already made a good start, you just need to extend the subclass's copy function:

class B(A):
    ...
    def copy(self):
        new_b = super().copy()  # new_b now has all the A stuff copied
        new_b.T = however_you_copy_a_T_instance(self.T)
        return new_b

Since addOn is just a method, there is no need to copy it - it's implicitly part of any B instance.

As an aside, if you implement your class's copying functions as __copy__() and __deepcopy__() then your class will work properly with the built in copy and deepcopy stuff provided by https://docs.python.org/3/library/copy.html (See the end of that page for more info).