Python Calculator App for Android using Kivy

Kivy is an open-source Python library for rapid development of applications that make use of innovative user interfaces, such as multi-touch apps. In this article, we will discuss how to create a simple calculator app for Android using Python and Kivy.

The Python programming language is known for its simplicity and ease of use, and with Kivy, it becomes even easier to create cross-platform apps. Kivy allows you to write your code once and run it on multiple platforms, including Android.

Creating the Calculator App

First, you need to have Kivy installed on your machine. You can do this by using pip:

		
			$ pip install kivy
		
	

Once you have Kivy installed, you can start creating the calculator app. We will use the Kivy language (KV) to define the user interface and Python to handle the logic of the calculator.

The KV file

Below is a simple example of how the KV file for the calculator app might look like:

		
<GridLayout>
	<TextInput id="display" font_size="30"/>
	<Button text="7" on_press="app.press('7')" />
	<Button text="8" on_press="app.press('8')" />
	<Button text="9" on_press="app.press('9')" />
	<Button text="+" on_press="app.press('+')" />
	<Button text="4" on_press="app.press('4')" />
	<Button text="5" on_press="app.press('5')" />
	<Button text="6" on_press="app.press('6')" />
	<Button text="-" on_press="app.press('-')" />
	<Button text="1" on_press="app.press('1')" />
	<Button text="2" on_press="app.press('2')" />
	<Button text="3" on_press="app.press('3')" />
	<Button text="*" on_press="app.press('*')" />
	<Button text="C" on_press="app.clear()" />
	<Button text="0" on_press="app.press('0')" />
	<Button text="=" on_press="app.calculate()" />
	<Button text="/" on_press="app.press('/')" />
</GridLayout>
		
	

The Python file

Now, let’s take a look at the Python file that implements the functionality of the calculator:

		
import kivy
from kivy.app import App
from kivy.uix.gridlayout import GridLayout
from kivy.uix.button import Button

class CalculatorApp(App):
	def build(self):
		self.display = TextInput(font_size=30)
		layout = GridLayout(cols=4)
		layout.add_widget(self.display)
		buttons = [
			"7", "8", "9", "+",
			"4", "5", "6", "-",
			"1", "2", "3", "*",
			"C", "0", "=", "/",
		]

		for button in buttons:
			btn = Button(text=button, on_press=self.press)
			layout.add_widget(btn)
			
		return layout

	def press(self, button):
		self.display.text += button

	def clear(self):
		self.display.text = ""

	def calculate(self):
		try:
			self.display.text = str(eval(self.display.text))
		except:
			self.display.text = "Error"

if __name__ == '__main__':
	CalculatorApp().run()
		
	

By combining the KV and Python files, you can create a simple yet functional calculator app for Android using Python and Kivy.

Once your app is ready, you can package it for distribution on the Google Play Store or use it for your personal use. The possibilities are endless with Python and Kivy!

Happy coding!