[lang-ref] ( composite_key ) ( python )

def test_composite_key():
    # use tuple
    d = {}
    d[(1, 2, 3)] = 'OK'
    assert d[(1, 2, 3)] == "OK"

    # while tuple is hashable, list is not.
    with pytest.raises(TypeError):
        d[[1, 2, 3]] = "NG"