>):</span>
            <span class="k">try</span><span class="p">:</span>
                <span class="n">x</span><span class="p">[</span><span class="n">index</span><span class="p">]</span> <span class="o">+=</span> <span class="n">x_i</span><span class="p">[</span><span class="n">i</span><span class="p">]</span>
            <span class="k">except</span> <span class="ne">IndexError</span><span class="p">:</span>
                <span class="n">x</span><span class="p">[</span><span class="n">index</span><sp