title: Update Python Dictionary with Tuple of Strings to set (key, value) fails
body: <p><a href="https://docs.python.org/3/library/stdtypes.html#dict.update" rel="nofollow noreferrer"><code>dict.update([other])</code></a> says</p>
  <blockquote>
  <p>Update the dictionary with the key/value pairs from <em>other</em>, overwriting existing keys. Return <em>None</em>.</p>
  <p>update() accepts either another dictionary object or an iterable of key/value pairs (as tuples or other iterables of length two). If keyword arguments are specified, the dictionary is then updated with those key/value pairs: d.update(red=1, blue=2).</p>
  </blockquote>
  <p>But</p>
  <pre><code>&gt;&gt;&gt; {}.update( (&quot;key&quot;, &quot;value&quot;) )
  Traceback (most recent call last):
    File &quot;&lt;stdin&gt;&quot;, line 1, in &lt;module&gt;
  ValueError: dictionary update sequence element #0 has length 3; 2 is required
  </code></pre>
  <p>So why does Python apparently try to use the first string of the tuple?</p>