how do I properly inherit from a superclass that has a __new__ method?

Question

Let\'s assume we have a class \'Parent\' , that for some reason has __new__ defined and a class \'Child\' that inherits from it. (In my case I\'m trying to inh

Answer 1

As I understand it, when you call Child("myarg", "otherarg"), that actually means something like this:

c = Child.__new__(Child, "myarg", "otherarg")
if isinstance(c, Child):
    c.__init__("myarg", "otherarg")

You could:

1. Write an alternative constructor, like Child.create_with_extra_arg("myarg", "otherarg"), which instantiates Child("otherarg") before doing whatever else it needs to.

2. Override Child.__new__, something like this:

.

def __new__(cls, myarg, argforsuperclass):
    c = Parent.__new__(cls, argforsuperclass)
    c.field = myarg
    return c

I haven't tested that. Overriding __new__ can quickly get confusing, so it's best to avoid it if possible.