Inheriting from immutable types [duplicate]

Answer 1

You can subclass int, but because it is immutable you need to provide a .__new__() constructor hook:

class MyInt(int):
    def __new__(cls, value):
        new_myint = super(MyInt, cls).__new__(cls, value)
        return new_myint

You do need to call the base __new__ constructor to get your subclass properly created.

In Python 3, you can omit the arguments to super() altogether:

class MyInt(int):
    def __new__(cls, value):
        new_myint = super().__new__(cls, value)
        return new_myint

Of course, this assumes you wanted to manipulate value before passing in to super().__new__() or manipulate new_myint some more before returning; otherwise you may as well remove the whole __new__ method and just implement this as class MyInt(int): pass.