is {:d}&quot;</span><span class="p">,</span> <span class="s">&quot;forty-two&quot;</span><span class="p">);</span>
</pre></div>
</div>
<p>throws a <code class="docutils literal"><span class="pre">format_error</span></code> exception with description &#8220;unknown format code &#8216;d&#8217; for
string&#8221;, because the argument <code class="docutils literal"><span class="pre">&quot;forty-two&quot;</span></code> is a string while the format code
<code class="docutils literal"><span class="pre">d</span></c