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    <p>If you want <code>out</code> to hold the values of the last list/tuple in <code>nodes</code> without them getting reset to <code>0.0</code> you need to either create a copy of that object (<code>nodes[-1]</code>) or manually copy them into a new list/tuple object, if I understand you correctly, and that's your aim. You are currently just creating a reference to nodes[-1] before you interate through the 2-dimensional array and reset all values to <code>0.0</code>, which means, <code>out</code> will still reference the referent in memory that you reset to <code>0.0</code> values.</p> <pre><code>out = nodes[-1].copy() # This is the list/tuple with the (non-reset) values that you want to return ... # iterate through the array here and reset return out </code></pre> <p>This will now return the <strong>copy</strong> (i.e. a new reference to a <em>new, unique</em> referent in memory) of the last element of <code>nodes</code> with the state it was in when you created the copy (before the reset iteration).</p> <p>Not sure if I understood you correctly but forgetting that lists and tuples <strong>are</strong> objects in Python and behave as such is an easy mistake to make.</p> <p>That means: l0 = [0, 1] l1 = l0 l2 = l0.copy() l0.append(2)</p> <pre><code>print(l0) # prints [0, 1, 2] print(l1) # prints [0, 1, 2] print(l2) # prints [0, 1] </code></pre> <p><code>l0</code> and <code>l1</code> are two references to the same object/referent in memory. Through the <code>copy()</code> operation <code>l2</code> becomes a reference to a unique and <em>non-identical</em> referent in memory.</p> <p><strong>Addition:</strong> Please note that list.copy() is, as kindly pointed out in the comments, available in Python 3 only and returns a shallow copy. Use <code>copy.copy()</code>/<code>copy.deepcopy()</code> to create a shallow/deep copy respectively; this module is available in <em>Python 2</em> and <em>Python 3</em>. Alternatively, a <em>shallow</em> copy of a list can be produced through <code>list(list_to_copy)</code>.</p> <p>Documentation here:</p> <ul> <li><a href="http://docs.python.org/2/library/copy.html" rel="nofollow">http://docs.python.org/2/library/copy.html</a></li> <li><a href="http://docs.python.org/3.3/library/copy.html" rel="nofollow">http://docs.python.org/3.3/library/copy.html</a></li> </ul>
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    1. CONote that the `list.copy` method was added in Python 3.
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    2. COThanks @JanneKarila, added your info and expanded on it.
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    3. COA simple way to copy a list is `list(nodes)`. Also I'd just drop that Python doesn't have a notion of "primitives"; every value is an object and that's it.
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