Python Kivy: Build a standard calculator application – Equals Button functionality
In this tutorial, we will learn how to add the Equals Button functionality to a standard calculator application using Python Kivy.
Step 1: Setting up the UI
First, let’s create a basic UI for the calculator. We will need buttons for numbers, operators, and the Equals button.
``` BoxLayout: TextInput: id: display font_size: 30 padding_x: 10 GridLayout: cols: 4 Button: text: '7' on_press: display.text += self.text Button: text: '8' on_press: display.text += self.text Button: text: '9' on_press: display.text += self.text Button: text: '/' on_press: display.text += self.text Button: text: '4' on_press: display.text += self.text Button: text: '5' on_press: display.text += self.text Button: text: '6' on_press: display.text += self.text Button: text: '*' on_press: display.text += self.text Button: text: '1' on_press: display.text += self.text Button: text: '2' on_press: display.text += self.text Button: text: '3' on_press: display.text += self.text Button: text: '-' on_press: display.text += self.text Button: text: 'C' on_press: display.text = '' Button: text: '0' on_press: display.text += self.text Button: text: '=' on_press: app.calculate() Button: text: '+' on_press: display.text += self.text ```
Step 2: Implementing the Equals Button functionality
Now, let’s implement the functionality for the Equals Button. When the user presses the Equals Button, we want the calculator to evaluate the expression and display the result.
``` def calculate(self): try: self.root.ids.display.text = str(eval(self.root.ids.display.text)) except: self.root.ids.display.text = 'Error' ```
With this code snippet, we define a method called calculate that uses the Python eval function to evaluate the expression in the calculator display. If the expression is valid, the result is displayed. If there is an error, such as division by zero, the display shows ‘Error’.
Conclusion
By following these steps, we have successfully added the Equals Button functionality to our standard calculator application using Python Kivy. Users can now input expressions and get the results with the click of a button.
