title: How to count number of rows, openpyxl
body: <p>We have an excel file. For example we have 2 column. A and B. In <em>A</em> we have - <strong>5</strong> rows in <em>B</em> - <strong>10</strong> rows. When we use function <code>len(ws['A'])</code> result is <strong>10</strong> (max of worksheet, not of column A only). Why <code>len()</code> works like that? Is it specificity of this function?</p>