将所需的位置参数传递给超类，而无需将其添加到子类的构造函数中

Question

I have such a class:

class C1:

    def __init__(self, arg1, kwarg1=1, kwarg2=2):
        ...

Now I want to create a C2 that just changes default values of kwarg1 and kwarg2 in C1 . It's some sort of functools.partial but for classes.

I can do it it this way:

class C2(C1):

    def __init__(self, arg1, kwarg1=3, kwarg2=4):
        super().__init(arg1, kwarg1=kwarg1, kwarg2=kwarg2)

But I don't like that I need to pass arg1 to C2 constructor and then pass it as it is to C1 with super().__init(arg1, ...) .

I'd like to do something like this:

class C2(C1):

    def __init__(self, kwarg1=3, kwarg2=4, *args, **kwargs):
        super().__init(kwarg1=kwarg1, kwarg2=kwarg2, *args, **kwargs)

but this doesn't work:

TypeError: __init__() missing 1 required positional argument: 'arg1'

Is there any way I can pass arg1 to C1 from C2 without mentioning it in C2 's constructor

Answer 1

You can do it on an even more convoluted way, but at least you won't be passing the dreaded arg1 :

class C2(C1):

    def __init__(self, *args, **kwargs):
        kwargs["kwarg1"] = kwargs.get("kwarg1", 3)
        kwargs["kwarg2"] = kwargs.get("kwarg2", 4)
        super().__init__(*args, **kwargs)

But you'll still need to keep your positional arguments when initializing C2 .