Kivy is a platform-independent GUI tool in Python. As it can be run on Android, IOS, linux and Windows etc. It is basically used to develop the Android application, but it does not mean that it can not be used on Desktops applications.
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In this article, we will learn how to make a simple calculator using Kivy.
Prerequisites:
1) Basic knowledge of Mathematics
2) Python
3) Kivy
4) Widgets and code understanding of 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
Implementation of the Approach:
main.py
Python3
# 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 buttons 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() |
calculator.kv
Python3
# 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 = ""
|
Output: