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    <p>I think what you're asking is how to test object <em>identity</em> rather than object <em>equality</em>.</p> <p>In Python you can do this with the <a href="http://docs.python.org/reference/expressions.html#is" rel="nofollow"><code>is</code> operator</a>, i.e.</p> <pre><code>if x is y: </code></pre> <p>Rather than:</p> <pre><code>if x == y: </code></pre> <p>However, you're going have problems with ints and strings because the Python runtime automatically re-uses objects it creates for these from a pool:</p> <pre><code>&gt;&gt;&gt; a = 1 &gt;&gt;&gt; b = 1 &gt;&gt;&gt; a is b True &gt;&gt;&gt; id(a),id(b) (13561552, 13561552) </code></pre> <p>I think short strings are automatically "interned" in this way and you can force longer strings to be using the <a href="http://docs.python.org/library/functions.html#intern" rel="nofollow"><code>intern()</code> function</a>:</p> <pre><code>&gt;&gt;&gt; c = 'Long string' &gt;&gt;&gt; d = 'Long string' &gt;&gt;&gt; c is d False &gt;&gt;&gt; c = intern(c) &gt;&gt;&gt; d = intern(d) &gt;&gt;&gt; c is d True </code></pre> <p>However, it seems the <code>long</code> type isn't interned so you use that:</p> <pre><code>&gt;&gt;&gt; a = 1L &gt;&gt;&gt; b = 1L &gt;&gt;&gt; a is b False </code></pre> <p>However, object identity for built-in types is down to the implementation of Python rather than being in the language, and is not something you should rely on either way. I think you would be better off creating your own class of objects and writing an appropriate <code>__eq__</code> method for them, i.e. write your code it works based on object equality rather than identity.</p>
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    1. USDave Webb
    1. USDave Webb
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    1. COSince Python reuses the same objects in memory for strings/numbers, do you think he could also use objects that store the values? eg `a = {'value':1}; b = {'value':1}` those are different objects and he can use the object references to do comparison and steal the value from `.value`. Or do you think `intern` is the better route?
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      1. USmeder omuraliev
    2. COSo, there's no way to force a number or string to initialize with its own unique identity?
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      1. USReznor
    3. CO@Reznor - you could take @meder's suggestion and create your own objects to store the values or you could use `long` which doesn't seem to be interned. However, if you are going to write your own class better to write one which behaves the way you want rather than relying on object identity which as we have seen is rather brittle.
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