Simple Calculator with Tkinter

Introduction

This document describes the implementation of a basic calculator using the Tkinter library in Python. The calculator supports basic arithmetic operations: addition, subtraction, multiplication, and division. It features a graphical user interface (GUI) with buttons for each digit, arithmetic operators, and a clear button.

Code Overview

The code provided creates a simple calculator application with the following functionalities:

• Number Entry: Buttons for digits 0-9.

• Operators: Buttons for addition (+), subtraction (-), multiplication (*), and division (/).

• Special Buttons: An equals button (=) to perform calculations and a clear button to reset the calculator.

Detailed Explanation

Importing Tkinter

from tkinter import *

The tkinter library is imported to create the graphical user interface (GUI) for the calculator.

Initializing the Main Window

window = Tk()
window.title("Simple Calculator")
window.geometry('500x330')

• Tk() initializes the main window of the application.

• window.title("Simple Calculator") sets the window title.

• window.geometry('500x330') defines the size of the window.

Global Variables

n1 = 0
n2 = 0
op = None
res = StringVar()

• n1 and n2 store the numbers used in calculations.

• op stores the current operator.

• res is a StringVar used to display results and updates in the GUI.

Functions

1. getvalue(a): Updates the number displayed based on button clicks.

    def getvalue(a):
        global n1, n2, res
        if op is None:
            number = n1 * 10 + a
            n1 = number
        else:
            number = n2 * 10 + a
            n2 = number
        res.set(str(number))
   

   • If no operator is selected, the function updates n1.

   • If an operator is selected, it updates n2.

2. getop(a): Sets the operator for the calculation.

    def getop(a):
        global op
        op = a
        res.set(str(op))
   

   • Sets the operator (+, -, *, /) and updates the display.

3. clears(): Resets the calculator.

    def clears():
        global n1, n2, op
        n1 = 0
        n2 = 0
        op = None
        res.set('0')
   

   • Resets n1, n2, and op to their initial values and updates the display to 0.

4. calculate(): Performs the calculation based on the selected operator.

    def calculate():
        if op == '-':
            res.set(str(n1 - n2))
        elif op == '+':
            res.set(str(n1 + n2))
        elif op == '/':
            res.set(str(n1 / n2))
        else:
            res.set(str(n1 * n2))
   

   • Performs the arithmetic operation based on op and updates the result.

GUI Elements

1. Display Area

    msg = Entry(window, bd=20, textvariable=res, relief='sunken', font=("Helvetica", 20))
    msg.grid(columnspan=4, ipadx=80, ipady=10)
   

   • Entry widget used to display the current value or result.

   • textvariable=res binds the display to the res variable.

2. Buttons

   Buttons are created for digits, operators, and special functions.

    button7 = Button(text=7, width=15, height="2", bg='lightgrey', command=lambda: getvalue(7))
    button7.grid(row=1, column=0, pady=1)
   

   • Button widget for digit 7 with command=lambda: getvalue(7) ensures the getvalue function is called with 7 as an argument.

Similar button creation is done for other digits, operators, and special functions like clear and equals.

Main Loop

mainloop()

• The mainloop() function starts the Tkinter event loop, making the application responsive to user interactions.

Summary

The provided code creates a functional GUI calculator using Tkinter. It handles basic arithmetic operations and provides a user-friendly interface for performing calculations. The use of Tkinter widgets such as Entry and Button allows for straightforward interaction and display of results.