title: Only allow values in a QTableWidget column
body: <p>If I have a really simple <a href="http://doc.qt.io/qt-4.8/qtablewidget.html" rel="nofollow noreferrer">QTableWidget</a> like the following:</p>
  
  <pre><code>data = ['first_row', 'second_row', 'third_row']
  
  qTable = self.dockwidget.tableWidget
  qTable.setRowCount(len(data))
  qTable.setColumnCount(2)
  
  for row in range(len(data)):
      for col in [0]:
          item = QTableWidgetItem(str(data[row]))
          qTable.setItem(row,col,item)
      for col in [1]:
          qTable.setItem(row,col,'0.1')
  </code></pre>
  
  <p>How could I make so that in the second column (where the default value is <code>0.1</code>), the user can only input values and not string?</p>