I’ve taken over some object-oriented Python code or questionable origin that I didn’t write and don’t fully understand. I have a question on object oriented inheritance behavior in Python that I’m seeing in this unfamiliar code. Here’s a minimal example of the issue that I’m struggling to understand:

class A:
    def __init__(self):
        self.a = "a"
        print("A.__init__()")


class B:
    def __init__(self):
        self.b = "b"
        print("B.__init__()")

class C:
    def __init__(self):
        self.c = "c"
        print("C.__init__()")


class X(A):
    def __init__(self):
        A.__init__(self)
        B.__init__(self)  # Note: B is not in X's inheritance list.
        C.__init__(self)  # Note: C is not in X's inheritance list.
        print("X.__init__()")


x = X()

If I run the code, it seems to run fine, and produces the expected output, in the expected order.

Question: What was the author’s intent when calling external initializers that are seemingly unrelated to the direct inheritance? Is this a reasonable thing to do in Python, and is there a common use case that involves this type of initialization pattern?

I don’t know why you would do this in Python.