How to make immutable classes in Python

immutable.py

#-*- coding: utf-8 -*-

from collections import namedtuple


class Immutable(namedtuple("Immutable", "x, y")):
    """Immutable class using collections.namedtuple."""
    def __str__(self):
        return "class: {c}, x: {x}, y: {y}".format(c=Immutable.__name__,
                                                   x=self.x, y=self.y)


class Immutable2(tuple):
    """Immutable class using tuple."""
    def __new__(cls, x, y):
        return tuple.__new__(cls, (x, y,))

    @property
    def x(self):
        return tuple.__getitem__(self, 0)

    @property
    def y(self):
        return tuple.__getitem__(self, 1)

    def __str__(self):
        return "class: {c}, x: {x}, y: {y}".format(c=Immutable2.__name__,
                                                   x=self.x, y=self.y)


class Immutable3(object):
    """Immutable class without overriding collections.namedtuple/tuple."""
    __slots__ = ("x", "y",)

    def __init__(self, x, y):
        object.__setattr__(self, "x", x)
        object.__setattr__(self, "y", y)

    def __setattr__(self, *args):
        raise AttributeError("Attributes of Immutable3 cannot be changed")

    def __delattr__(self, *args):
        raise AttributeError("Attributes of Immutable3 cannot be deleted")

    def __str__(self):
        return "class: {c}, x: {x}, y: {y}".format(c=Immutable3.__name__,
                                                   x=self.x, y=self.y)


if __name__ == "__main__":
    i1 = Immutable(1, 2)
    print(str(i1))
    try:
        i1.x = 3  # will fail
    except Exception:
        print("error while setting attribute of "
              "{0} object".format(Immutable.__name__))

    i2 = Immutable2(10, 20)
    print(str(i2))
    try:
        i2.x = 30  # will fail
    except Exception:
        print("error while setting attribute of "
              "{0} object".format(Immutable2.__name__))

    i3 = Immutable3(100, 200)
    print(str(i3))
    try:
        i3.x = 300  # will fail
    except Exception:
        print("error while setting attribute of "
              "{0} object".format(Immutable3.__name__))

Congrats for the example. I tried using the first example.
But I still have one question: how would I call a "check" method in the constructor and raise an error in case the args were incosistent.
For example:
Checking an ISS last two digits to see whether it is correct and raise an error (case the last two digits is not correct).