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    <p>The easiest way to do this is using <code>__slots__</code>:</p> <pre><code>class A(object): __slots__ = [] </code></pre> <p>Instances of <code>A</code> are immutable now, since you can't set any attributes on them.</p> <p>If you want the class instances to contain data, you can combine this with deriving from <code>tuple</code>:</p> <pre><code>from operator import itemgetter class Point(tuple): __slots__ = [] def __new__(cls, x, y): return tuple.__new__(cls, (x, y)) x = property(itemgetter(0)) y = property(itemgetter(1)) p = Point(2, 3) p.x # 2 p.y # 3 </code></pre> <p><strong>Edit</strong>: If you want to get rid of indexing either, you can override <code>__getitem__()</code>:</p> <pre><code>class Point(tuple): __slots__ = [] def __new__(cls, x, y): return tuple.__new__(cls, (x, y)) @property def x(self): return tuple.__getitem__(self, 0) @property def y(self): return tuple.__getitem__(self, 1) def __getitem__(self, item): raise TypeError </code></pre> <p>Note that you can't use <code>operator.itemgetter</code> for the properties in thise case, since this would rely on <code>Point.__getitem__()</code> instead of <code>tuple.__getitem__()</code>. Fuerthermore this won't prevent the use of <code>tuple.__getitem__(p, 0)</code>, but I can hardly imagine how this should constitute a problem.</p> <p>I don't think the "right" way of creating an immutable object is writing a C extension. Python usually relies on library implementers and library users being <a href="http://mail.python.org/pipermail/tutor/2003-October/025932.html" rel="noreferrer">consenting adults</a>, and instead of really enforcing an interface, the interface should be clearly stated in the documentation. This is why I don't consider the possibility of circumventing an overridden <code>__setattr__()</code> by calling <code>object.__setattr__()</code> a problem. If someone does this, it's on her own risk.</p>
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    1. POHow to make an immutable object in Python?
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    1. USSven Marnach
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    1. COWouldn't it be a better idea to use a `tuple` here, `__slots__ = ()`, rather than `__slots__ = []`? (Just clarifying)
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    2. CO@sukhbir: I think this does not matter at all. Why would you prefer a tuple?
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    3. CO@Sven: I agree it wouldn't matter (except the speed part, which we can ignore), but I thought of it this way: `__slots__` is not going to be changed right? It's purpose is to identify for once which attributes can be set. So doesn't a `tuple` seem a much *natural* choice in such a case?
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