title: How to update Qlabel with QCombobox without using a pushButton signal
body: <p>I was wondering how to add or update a qlabel from the combobox automatically. As i change the options in the QComboBox the QLabel should update.</p>
  
  <pre><code>convert_options = ["Celcius to Farenheit", "Celcius to Kelvin", "Farenheit to Celcius", "Farenheit to Kelvin", "Kelvin to Celcius", "Kelvin to Farenheit"]   
  
  
  
  class Frame(QWidget):
       def __init__(self):
              super(Frame, self).__init__()
              uic.loadUi("temperature_converter.ui", self)
              self.initUI()
  
   def initUI(self):
      self.setWindowTitle("Temperature Converter")
      self.comboBox_choices.addItems(convert_options)
      # comboText = self.comboBox_choices.currentText()
      # self.unit_choice(comboText)
      self.button_choices()
  
  # This if statement if used needs a button signal  
  
  def unit_choice(self, comboText):
          if comboText == "Celcius to Farenheit":
              self.label_unit.setText(chr(176) + "C")
          elif comboText == "Celcius to Kelvin":
              self.label_unit.setText(chr(176) + "C")
          elif comboText == "Farenheit to Celcius":
              self.label_unit.setText(chr(176) + "F")
          elif comboText == "Farenheit to Kelvin":
              self.label_unit.setText(chr(176) + "F")
          elif comboText == "Kelvin to Celcius":
              self.label_unit.setText(chr(176) + "K")
          elif comboText == "Kelvin to Farenheit":
              self.label_unit.setText(chr(176) + "K")
  </code></pre>