r</span><span class="p">()</span> <span class="ow">and</span> <span class="s1">&#39;by&#39;</span> <span class="ow">in</span> <span class="n">step</span><span class="o">.</span><span class="n">lower</span><span class="p">():</span>
            <span class="n">ilist</span> <span class="o">=</span> <span class="n">np</span><span class="o">.</span><span class="n">arange</span><span class="p">(</span><span class="nb">int</span><span class="p">(</span><span class="n">steps</span><span class="p">[</span><span cla