[lang-ref] ( immutable_set ) ( python )

def test_immutable_set():
    # frozenset
    items_set       = {'A', 'B', 'C'}
    items_frozenset = frozenset({'A', 'B', 'C'})

    items_set.add('D')

    with pytest.raises(AttributeError):
        items_frozenset.add('D')  # cannot be modified