Calculadora: configurando o "backspace" do display no botão "◀" (D)

aula202-calculadora/buttons.py

@@ -30,7 +30,7 @@ class ButtonsGrid(QGridLayout):
         super().__init__(*args, **kwargs)
 
         self._gridMask = [
-            ['C', '◀', '^', '/'],
+            ['C', 'D', '^', '/'],
             ['7', '8', '9', '*'],
             ['4', '5', '6', '-'],
             ['1', '2', '3', '+'],
@@ -78,6 +78,9 @@ class ButtonsGrid(QGridLayout):
         if text == 'C':
             self._connectButtonClicked(button, self._clear)
 
+        if text in 'D':
+            self._connectButtonClicked(button, self.display.backspace)
+
         if text in '+-/*^':
             self._connectButtonClicked(
                 button,