, <tt>Derived</tt> objects which have been passed to Python via a pointer or reference to <tt>Base</tt> can be passed where a pointer or reference to <tt>Derived</tt> is expected.</li></ol><p>

Now, we shall expose the C++ free functions <tt>b</tt> and <tt>d</tt> and <tt>factory</tt>:</p>

<code><pre>

    <span class=identifier>def</span><span class=special>(</span><span class=string>&quot;b&quot;</span><span class=special>, </span><span class=identifier>b</span><span class=special>);

    </span><span