Python, without classes.

noclasses.py

def _suspend_self(namespace, suspended):
    """
    Suspends a function, so that it has a self.

    :param namespace: The self namespace to use.
    :return: A function that will call the next function with self.
    """

    def suspender(*args, **kwargs):
        return suspended(namespace, *args, **kwargs)

    suspender.__name__ = suspended.__name__
    suspender.__defaults__ = suspended.__defaults__
    suspender.__signature__ = getattr(suspended, "__signature__", None)
    return suspender


def make_class(locals: dict):
    """
    Makes a class, from the locals of the callee.

    :param locals: The locals to build the class from.
    """

    # try and find a `__call__` to implement the call function
    # this is made as a function so that namespace and called can refer to eachother
    def call_maker():
        if '__call__' in locals and callable(locals['__call__']):
            return _suspend_self(namespace, locals['__call__'])

        def _not_callable(*args, **kwargs):
            raise TypeError('This is not callable')

        return _not_callable

    # this acts as the "self" object
    # all attributes are set on this
    def namespace():
        return called()

    # get the callable function that namespace delegates to
    # this is called afterwards so that call_maker has the chance to load namespace from cellvars
    called = call_maker()

    # make an init substitute function
    def new_class(*args, **kwargs):
        init = locals.get("__init__")
        if init is not None:
            init(namespace, *args, **kwargs)

        return namespace

    # update namespace
    for name, item in locals.items():
        if callable(item):
            fn = _suspend_self(namespace, item)
            setattr(namespace, name, fn)

    return new_class


def make(fn):
    """
    Makes a class from a function. Example usage:

    .. code-block:: python

        from noclasses import make_class, make

        @make
        def MyClass():
            def __init__(self, first, second):
                self.first = first
                self.second = second

            def add(self):
                return self.first + self.second

            return make_class(locals())

        instance = MyClass(2, 2)
        print(instance.add())  # 4

    """
    return fn()

This is invalid. You assign attributes directly to the class, not to instances. Example:

instance = MyClass(2, 2)
instance2 = MyClass(3, 3)
print(instance.add())  # 6 but should be 4