simple_kv.kv

BoxLayout:
    orientation: "vertical"
    Label:
        text: "Result of Addition."
        id: label
    BoxLayout:
        orientation: "horizontal"
        TextInput:
            hint_text: "Enter First Number."
            id: textinput1
        TextInput:
            hint_text: "Enter Second Number."
            id: textinput2
    Button:
        text: "Add Numbers."
        on_press: app.add_nums(root)