How to Create a Simple Calculator using Python

Python / March 24, 2019

In this tutorial, I’ll show you how to create a simple calculator using Python.

First, I’ll share the source code that you can use right away.

Then, I’ll perform a quick demonstration to show you how to use the calculator. And finally, I’ll explain each component that was used in the code to build the calculator in Python.

This is how the calculator would look like:

How to Create a Simple Calculator using Python

Source Code to Create the Calculator using Python

You may run the following source code in Python in order to launch the calculator:

import tkinter as tk

root= tk.Tk()

canvas1 = tk.Canvas(root, width = 300, height = 300)
canvas1.pack()

entry1 = tk.Entry (root) 
canvas1.create_window(210, 100, window=entry1)

entry2 = tk.Entry (root) 
canvas1.create_window(210, 140, window=entry2)

entry3 = tk.Entry (root) 
canvas1.create_window(210, 240, window=entry3)

label0 = tk.Label(root, text='Calculator')
label0.config(font=('helvetica', 14))
canvas1.create_window(150, 40, window=label0)

label1 = tk.Label(root, text='Type Value 1:')
label1.config(font=('helvetica', 10))
canvas1.create_window(100, 100, window=label1)

label2 = tk.Label(root, text='Type Value 2:')
label2.config(font=('helvetica', 10))
canvas1.create_window(100, 140, window=label2)

label3 = tk.Label(root, text='Result:')
label3.config(font=('helvetica', 10))
canvas1.create_window(100, 240, window=label3)

def add():  
    v1 = entry1.get()
    v2 = entry2.get()
  
    label4 = tk.Label(root, text= float(v1)+float(v2),font=('helvetica', 10, 'bold'),bg='white')
    canvas1.create_window(210, 240, window=label4)
      
buttonAdd = tk.Button(text='+', command=add, bg='green', fg='white', font=('helvetica', 9, 'bold'), width = 5)
canvas1.create_window(90, 190, window=buttonAdd)

def sub():  
    v1 = entry1.get()
    v2 = entry2.get()
  
    label5 = tk.Label(root, text= float(v1)-float(v2),font=('helvetica', 10, 'bold'),bg='white')
    canvas1.create_window(210, 240, window=label5)
      
buttonSub = tk.Button(text='–', command=sub, bg='green', fg='white', font=('helvetica', 9, 'bold'), width = 5)
canvas1.create_window(140, 190, window=buttonSub)

def mul():  
    v1 = entry1.get()
    v2 = entry2.get()
  
    label6 = tk.Label(root, text= float(v1)*float(v2),font=('helvetica', 10, 'bold'),bg='white')
    canvas1.create_window(210, 240, window=label6)
      
buttonMul = tk.Button(text='x', command=mul, bg='green', fg='white', font=('helvetica', 9, 'bold'), width = 5)
canvas1.create_window(190, 190, window=buttonMul)

def div():  
    v1 = entry1.get()
    v2 = entry2.get()
  
    label7 = tk.Label(root, text= float(v1)/float(v2),font=('helvetica', 10, 'bold'),bg='white')
    canvas1.create_window(210, 240, window=label7)
      
buttonDiv = tk.Button(text='/', command=div, bg='green', fg='white', font=('helvetica', 9, 'bold'), width = 5)
canvas1.create_window(240, 190, window=buttonDiv)

root.mainloop()

Using the Calculator

You should now see the following display:

How to Create a Simple Calculator using Python

Let’s say that you want to sum the values of 4 and 3. You can then type those values in the entry boxes, and then click on the ‘+’ button to add those values:

Simple Calculator using Python

The result that you’ll get is 7. Which is indeed the sum of 4 and 3:

math symbols

And if you decide to multiply those values instead, then simply click on the ‘x’ to multiply the values and you’ll get the result of 12:

tkinter

In the final section, I’ll explain each component that was used in the code.

How to Build the Calculator in Python

Import the tkinter package and create the Canvas

The first thing that you’ll need to do is to import the tkinter package. The tkinter package can be used to create a Graphical User Interface (GUI) in Python.

You’ll also need to add the canvas, which is your GUI display in which you can place items, such as buttons, entry boxes, etc.

import tkinter as tk

root= tk.Tk()

canvas1 = tk.Canvas(root, width = 300, height = 300)
canvas1.pack()

Create the entry boxes

Next, you’ll need to create the entry boxes to collect the data from the user.

The first two entry boxes are used to collect the Value 1 and Value 2. While the third entry box is just for visual purposes, where the result of the calculation will be displayed.

entry1 = tk.Entry (root) 
canvas1.create_window(210, 100, window=entry1)

entry2 = tk.Entry (root) 
canvas1.create_window(210, 140, window=entry2)

entry3 = tk.Entry (root) 
canvas1.create_window(210, 240, window=entry3)

Add the labels

There are 4 labels that are currently displayed on the GUI:

  • Calculator
  • Type Value 1:
  • Type Value 2:
  • Result:

You may edit the text, format and/or location where the labels will be displayed.

label0 = tk.Label(root, text='Calculator')
label0.config(font=('helvetica', 14))
canvas1.create_window(150, 40, window=label0)

label1 = tk.Label(root, text='Type Value 1:')
label1.config(font=('helvetica', 10))
canvas1.create_window(100, 100, window=label1)

label2 = tk.Label(root, text='Type Value 2:')
label2.config(font=('helvetica', 10))
canvas1.create_window(100, 140, window=label2)

label3 = tk.Label(root, text='Result:')
label3.config(font=('helvetica', 10))
canvas1.create_window(100, 240, window=label3)

Create the functions and buttons

There are 4 functions in the code:

  • add – to add the values
  • sub – to subtract the values
  • mul – to multiply the values
  • div – to divide the values

For each of those 4 functions, there is an associated button that can be used to trigger the function. For example, the ‘buttonAdd’ will trigger the add function to add the values that the user typed in the entry boxes.

def add():  
    v1 = entry1.get()
    v2 = entry2.get()
  
    label4 = tk.Label(root, text= float(v1)+float(v2),font=('helvetica', 10, 'bold'),bg='white')
    canvas1.create_window(210, 240, window=label4)
      
buttonAdd = tk.Button(text='+', command=add, bg='green', fg='white', font=('helvetica', 9, 'bold'), width = 5)
canvas1.create_window(90, 190, window=buttonAdd)

def sub():  
    v1 = entry1.get()
    v2 = entry2.get()
  
    label5 = tk.Label(root, text= float(v1)-float(v2),font=('helvetica', 10, 'bold'),bg='white')
    canvas1.create_window(210, 240, window=label5)
      
buttonSub = tk.Button(text='–', command=sub, bg='green', fg='white', font=('helvetica', 9, 'bold'), width = 5)
canvas1.create_window(140, 190, window=buttonSub)

def mul():  
    v1 = entry1.get()
    v2 = entry2.get()
  
    label6 = tk.Label(root, text= float(v1)*float(v2),font=('helvetica', 10, 'bold'),bg='white')
    canvas1.create_window(210, 240, window=label6)
      
buttonMul = tk.Button(text='x', command=mul, bg='green', fg='white', font=('helvetica', 9, 'bold'), width = 5)
canvas1.create_window(190, 190, window=buttonMul)

def div():  
    v1 = entry1.get()
    v2 = entry2.get()
  
    label7 = tk.Label(root, text= float(v1)/float(v2),font=('helvetica', 10, 'bold'),bg='white')
    canvas1.create_window(210, 240, window=label7)
      
buttonDiv = tk.Button(text='/', command=div, bg='green', fg='white', font=('helvetica', 9, 'bold'), width = 5)
canvas1.create_window(240, 190, window=buttonDiv)

root.mainloop()

Don’t forget to add the root.mainloop() at the end.