Strings weren't mutable, they said.

ref.py

import typing as t

def ref(obj):
    class Ref:
        pass

    slf = Ref()
    slf.__obj = obj

    build_methods(slf)
    return slf

def build_methods(slf):
    obj = slf.__obj
    Ref = type(slf)
    def make_ref_meth(orig_meth):
        def ref_meth(*args, **kwargs):
            if args and type(args[0]) is Ref:
                return orig_meth(slf.__obj, *args[1:], **kwargs)
            else:
                return orig_meth(*args, **kwargs)
        return ref_meth

    def make_inplace_meth(ref_meth):
        def inplace_meth(slf, *args, **kwargs):
            oldtyp = type(slf.__obj)
            slf.__obj = ref_meth(slf, *args, **kwargs)
            if oldtyp is not type(slf.__obj):
                build_methods(slf)
            return slf
        return inplace_meth

    for k, v in vars(type(obj)).items():
        if k in ["__getattribute__"]:
            continue

        if isinstance(v, t.Callable):
            setattr(Ref, k, ref_meth := make_ref_meth(v))
            if k.startswith("__") and k.endswith("__"):
                name = k[2:-2]
                if name.startswith("i"):
                    continue
                inplace_name = f"__i{name}__"
                if hasattr(type(obj), inplace_name):
                    continue
                setattr(Ref, inplace_name, make_inplace_meth(ref_meth))
        else:
            setattr(Ref, k, v)

    return slf

string = ref("hello")
num = ref(1)

def double(val):
    val += val

double(num)
double(string)
print(num)  # 2
print(string) # hellohello