code: def wheelEvent(self, event):
          
  
          if event.modifiers() == Qt.ControlModifier:
              if event.delta() == 120:
                  self.zoom_in()
              elif event.delta() == -120:
                  self.zoom_out()
              event.ignore()
          else:
              QPlainTextEdit.wheelEvent(self, event)
docs: Reimplements the :meth:`QPlainTextEdit.wheelEvent` method.
  
          :param event: Event.
          :type event: QEvent