Cómo hacer una calculadora usando kivy | Python

Kivy es una herramienta GUI independiente de la plataforma en Python. Como se puede ejecutar en Android, IOS, Linux y Windows, etc. Básicamente se usa para desarrollar la aplicación de Android, pero eso no significa que no se pueda usar en aplicaciones de escritorio.
 

????????? Tutorial de Kivy: aprenda Kivy con ejemplos .

En este artículo, aprenderemos cómo hacer una calculadora simple usando Kivy.
 

Prerrequisitos:
1) Conocimiento básico de Matemáticas 
2) Python 
3) Kivy 
4) Widgets y comprensión del código de kivy

Basic approach to make A calculator:

1) import kivy
2) import kivyApp
3) import Gridlayout
4) import config(to configure/adjust the window size)
5) Set minimum version(optional)
6) Create Layout class :
      define Calculator function in it
         : In this i am using try-catch because if any arithmetic 
            exception occur it will through the error  

7) create App class
8) create .kv file (name same as the app class):
        1) create buttons
        2) Add the style to the buttons
        3) Add functionalities of the button 
9) return Layout/widget/Class(according to requirement)
10) Run an instance of the class

Implementación del Enfoque: 
main.py
 

# Program to create a calculator
   
# Program to Show how to create a switch
# import kivy module   
import kivy 
      
# base Class of your App inherits from the App class.   
# app:always refers to the instance of your application  
from kivy.app import App
    
# this restrict the kivy version i.e 
# below this kivy version you cannot 
# use the app or software 
kivy.require('1.9.0')
 
# for making multiple bttons to arranging
# them we are using this
from kivy.uix.gridlayout import GridLayout
 
# for the size of window
from kivy.config import Config
 
# Setting size to resizable
Config.set('graphics', 'resizable', 1)
## Config.set('graphics', 'width', '400')
## Config.set('graphics', 'height', '400')
 
 
# Creating Layout class
class CalcGridLayout(GridLayout):
  
    # Function called when equals is pressed
    def calculate(self, calculation):
        if calculation:
            try:
                # Solve formula and display it in entry
                # which is pointed at by display
                self.display.text = str(eval(calculation))
            except Exception:
                self.display.text = "Error"
  
 # Creating App class
class CalculatorApp(App):
  
    def build(self):
        return CalcGridLayout()
  
# creating object and running it
calcApp = CalculatorApp()
calcApp.run()

  
calculadora.kv
 

# Custom button
<CustButton@Button>:
    font_size: 32
  
# Define id so I can refer to the CalcGridLayout
# class functions
# Display points to the entry widget
<CalcGridLayout>:
    id: calculator
    display: entry
    rows: 6
    padding: 10
    spacing: 10
 
     
  
    # Where input is displayed
    BoxLayout:
        TextInput:
            id: entry
            font_size: 32
            multiline: False
  
    # When buttons are pressed update the entry
    BoxLayout:
        spacing: 10
        CustButton:
            text: "7"
            on_press: entry.text += self.text
        CustButton:
            text: "8"
            on_press: entry.text += self.text
        CustButton:
            text: "9"
            on_press: entry.text += self.text
        CustButton:
            text: "+"
            on_press: entry.text += self.text
  
    BoxLayout:
        spacing: 10
        CustButton:
            text: "4"
            on_press: entry.text += self.text
        CustButton:
            text: "5"
            on_press: entry.text += self.text
        CustButton:
            text: "6"
            on_press: entry.text += self.text
        CustButton:
            text: "-"
            on_press: entry.text += self.text
  
    BoxLayout:
        spacing: 10
        CustButton:
            text: "1"
            on_press: entry.text += self.text
        CustButton:
            text: "2"
            on_press: entry.text += self.text
        CustButton:
            text: "3"
            on_press: entry.text += self.text
        CustButton:
            text: "*"
            on_press: entry.text += self.text
  
    # When equals is pressed pass text in the entry
    # to the calculate function
    BoxLayout:
        spacing: 10
        CustButton:
            text: "AC"
            on_press: entry.text = ""
        CustButton:
            text: "0"
            on_press: entry.text += self.text
        CustButton:
            text: "="
            on_press: calculator.calculate(entry.text)
        CustButton:
            text: "/"
            on_press: entry.text += self.text
    BoxLayout:
        CustButton:
            font_size: 20
            text: "Scientific calculator"
            on_press: entry.text = ""       

Producción: