Python: how to change (last) element of tuple?
<p>The question is a bit misleading, because a tuple is <em>immutable</em>. What I want is: </p>

<p>Having a tuple <code>a = (1, 2, 3, 4)</code> get a tuple <code>b</code> that is exactly like <code>a</code> except for the last argument which is, say, twice the last element of <code>a</code>.</p>

<p>=> b == (1, 2, 3, 8)</p>
