title: How to get cell value from selected row (QTableView)?
body: <p>I have a <code>QTableView</code> and I need to the get value (string) from the first cell of the selected row (any cell on the row could be selected). But I need this value <em>only if exactly one row was selected</em>.</p>
  
  <p>I thought - I need to get index of the selected row and then get the value of the first сell on that line, but I couldn't find a way to do it.</p>