gistfile1.txt

_setattr_cached = object.__setattr__

class A:
    __slots__ = ('x', 'y', 'z', 'a', 'b', 'c')

    def __init__(self, x, y, z, a, b, c):
        _setattr = _setattr_cached.__get__(self, A)
        _setattr('x', x)
        _setattr('y', y)
        _setattr('z', z)
        _setattr('a', a)
        _setattr('b', b)
        _setattr('c', c)

    def __setattr__(self, name, value):
        raise AttributeError