immutable objects in Python that can have weak references

Question

I've been subclassing tuple or using namedtuple blissfully for a few years, but now I have a use case where I need a class that can be used as a weak referent. And today I learned tuples don't support weak references.

Is there another way to create an immutable object in Python with a fixed set of attributes? I don't need the numeric indexing or variable width of a tuple.

class SimpleThingWithMethods(object):
    def __init__(self, n, x):
        # I just need to store n and x as read-only attributes 
    ... ??? ...

---

I guess this raises the obvious question of why immutable; "Pythonic" code usually just assumes we're all adults here and no one in their right mind would reach into a class and muck with its values if it risks ruining the class invariants. In my case I have a class in a library and I am worried about accidental modification of objects by end-users. The people I work with sometimes make incorrect assumptions about my code and start doing things I did not expect, so it's much cleaner if I can raise an error if they accidentally modify my code.

I'm not so worried about bulletproof immutability; if someone really nefarious wants to go and modify things, ok, fine, they're on their own. I just want to make it hard to accidentally modify my objects.

Answer 1

well, this isn't a great answer but it looks like I can modify the answer in https://stackoverflow.com/a/4828492/44330 --- essentially overriding __setattr__ and __delattr__ to meet my needs at least against accidental modification. (but not as nice as subclassing tuple)

class Point(object):
    __slots__ = ('x','y','__weakref__')
    def __init__(self, x, y):
        object.__setattr__(self, "x", x)
        object.__setattr__(self, "y", y)
    def __setattr__(self, *args):
        raise TypeError
    def __delattr__(self, *args):
        raise TypeError
    def __eq__(self, other):
        return self.x == other.x and self.y == other.y
    def __hash__(self):
        return self.x.__hash__() * 31 + self.y.__hash__()

Implementing @Elazar's idea:

class Point(object):
    __slots__ = ('x','y','__weakref__')
    def __new__(cls, x, y):
        thing = object.__new__(cls) 
        object.__setattr__(thing, "x", x)
        object.__setattr__(thing, "y", y)
        return thing
    def __setattr__(self, *args):
        raise TypeError
    def __delattr__(self, *args):
        raise TypeError
    def __eq__(self, other):
        return self.x == other.x and self.y == other.y
    def __hash__(self):
        return self.x.__hash__() * 31 + self.y.__hash__()