from kivy.app import App

from kivy.uix.boxlayout import BoxLayout

from kivy.uix.button import Button

from kivy.uix.textinput import TextInput

​

​

class CalculatorApp(App):

    def build(self):

        self.icon = "calculator.png"

        self.operators = ["/", "*", "+", "-"]

        self.last_was_operator = None

        self.last_button = None

        self.solution = TextInput(background_color="black", foreground_color="white", readonly=True)

        main_layout = BoxLayout(orientation="vertical")

        main_layout.add_widget(self.solution)

​

        buttons = [

            ["7", "8", "9", "/"],

            ["4", "5", "6", "*"],

            ["1", "2", "3", "+"],

            [".", "0", "C", "-"],

        ]

​

        for row in buttons:

            h_layout = BoxLayout()

            for label in row:

                button = Button(

                    text=label, font_size=30, background_color="grey",

                    pos_hint={"center_x": 0.5, "center_y": 0.5}

                )

                if label == "C":

                    button.bind(on_press=self.clear_text)

                else:

                    button.bind(on_press=self.button_press)

                h_layout.add_widget(button)

            main_layout.add_widget(h_layout)

​

        equal_button = Button(

            text="=", font_size=30, background_color="grey",

            pos_hint={"center_x": 0.5, "center_y": 0.5}

        )

        equal_button.bind(on_press=self.calculate)

        main_layout.add_widget(equal_button)

​

        return main_layout

​

    def button_press(self, instance):

        current_text = self.solution.text

        button_text = instance.text

​

        if button_text in self.operators:

            if self.last_was_operator:

                return

            elif current_text == "":

                return

​

            self.last_was_operator = True

            self.solution.text += button_text

        else:

            self.last_was_operator = False

            self.solution.text += button_text

​

    def calculate(self, instance):

        current_text = self.solution.text

        if current_text:

            try:

                self.solution.text = str(eval(current_text))

            except Exception:

                self.solution.text = "Error"

​

    def clear_text(self, instance):

        self.solution.text = ""

​

​

if __name__ == "__main__":

    app = CalculatorApp()

    app.run()