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Calculator Application using Tkinter

In this tutorial, we will cover how to create a simple calculator app using Python Tkinter.

As in our previous tutorials, we have covered how to create tkinter buttons, tkinter labels, tkinter entry, tkinter frames and tkinter checkbuttons, and many more. Now with the help of all the widgets discussed in previous sections, we are going to create a Calculator App using Tkinter.

Here is how our calculator will look, which is made by using the input field, buttons and for the calculation purpose we will use logic in our code defined in functions, like if you want to add two numbers then behind this there must be a logic for addition purpose, similarly for substraction, multiplication, etc, we have created functions whose task is to perform these operations.

Calculator app with Tkinter

We have an Input Field in which the user input will be shown and the final result of the calculation will be displayed.

And the buttons are like 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, +, -, *, /, =, ., and C(clear button)

What is a Calculator?

For those who do not know, a calculator is basically a program on a computer that simulates the behavior of any hand-held calculator useful for performing Mathematical Calculations. It is a very basic device used in our every day lives. Now all the smartphones also have a Calculator application in them.

While creating any GUI Application there are mainly two steps:

  • The first step is to create a User Interface.

  • The second step is the most important one and in this, to add functionalities to the GUI

Now let's begin with creating a simple calculator app using Tkinter in Python which is used for basic arithmetic calculations.

Calculator App Code

Now it's time to take a look at the code to create a Calculator App using Tkinter:

from tkinter import *

win = Tk() # This is to create a basic window
win.geometry("312x324")  # this is for the size of the window 
win.resizable(0, 0)  # this is to prevent from resizing the window
win.title("Calculator")

###################Starting with functions ####################
# 'btn_click' function : 
# This Function continuously updates the 
# input field whenever you enters a number

def btn_click(item):
    global expression
    expression = expression + str(item)
    input_text.set(expression)

# 'bt_clear' function :This is used to clear 
# the input field

def bt_clear(): 
    global expression 
    expression = "" 
    input_text.set("")
 
# 'bt_equal':This method calculates the expression 
# present in input field
 
def bt_equal():
    global expression
    result = str(eval(expression)) # 'eval':This function is used to evaluates the string expression directly
    input_text.set(result)
    expression = ""
 
expression = ""
 
# 'StringVar()' :It is used to get the instance of input field
 
input_text = StringVar()
 
# Let us creating a frame for the input field
 
input_frame = Frame(win, width=312, height=50, bd=0, highlightbackground="black", highlightcolor="black", highlightthickness=2)
 
input_frame.pack(side=TOP)
 
#Let us create a input field inside the 'Frame'
 
input_field = Entry(input_frame, font=('arial', 18, 'bold'), textvariable=input_text, width=50, bg="#eee", bd=0, justify=RIGHT)
 
input_field.grid(row=0, column=0)
 
input_field.pack(ipady=10) # 'ipady' is internal padding to increase the height of input field
 
#Let us creating another 'Frame' for the button below the 'input_frame'
 
btns_frame = Frame(win, width=312, height=272.5, bg="grey")
 
btns_frame.pack()
 
# first row
 
clear = Button(btns_frame, text = "C", fg = "black", width = 32, height = 3, bd = 0, bg = "#eee", cursor = "hand2", command = lambda: bt_clear()).grid(row = 0, column = 0, columnspan = 3, padx = 1, pady = 1)
 
divide = Button(btns_frame, text = "/", fg = "black", width = 10, height = 3, bd = 0, bg = "#eee", cursor = "hand2", command = lambda: btn_click("/")).grid(row = 0, column = 3, padx = 1, pady = 1)
 
# second row
 
seven = Button(btns_frame, text = "7", fg = "black", width = 10, height = 3, bd = 0, bg = "#fff", cursor = "hand2", command = lambda: btn_click(7)).grid(row = 1, column = 0, padx = 1, pady = 1)
 
eight = Button(btns_frame, text = "8", fg = "black", width = 10, height = 3, bd = 0, bg = "#fff", cursor = "hand2", command = lambda: btn_click(8)).grid(row = 1, column = 1, padx = 1, pady = 1)
 
nine = Button(btns_frame, text = "9", fg = "black", width = 10, height = 3, bd = 0, bg = "#fff", cursor = "hand2", command = lambda: btn_click(9)).grid(row = 1, column = 2, padx = 1, pady = 1)
 
multiply = Button(btns_frame, text = "*", fg = "black", width = 10, height = 3, bd = 0, bg = "#eee", cursor = "hand2", command = lambda: btn_click("*")).grid(row = 1, column = 3, padx = 1, pady = 1)
 
# third row
 
four = Button(btns_frame, text = "4", fg = "black", width = 10, height = 3, bd = 0, bg = "#fff", cursor = "hand2", command = lambda: btn_click(4)).grid(row = 2, column = 0, padx = 1, pady = 1)
 
five = Button(btns_frame, text = "5", fg = "black", width = 10, height = 3, bd = 0, bg = "#fff", cursor = "hand2", command = lambda: btn_click(5)).grid(row = 2, column = 1, padx = 1, pady = 1)
 
six = Button(btns_frame, text = "6", fg = "black", width = 10, height = 3, bd = 0, bg = "#fff", cursor = "hand2", command = lambda: btn_click(6)).grid(row = 2, column = 2, padx = 1, pady = 1)
 
minus = Button(btns_frame, text = "-", fg = "black", width = 10, height = 3, bd = 0, bg = "#eee", cursor = "hand2", command = lambda: btn_click("-")).grid(row = 2, column = 3, padx = 1, pady = 1)
 
# fourth row
 
one = Button(btns_frame, text = "1", fg = "black", width = 10, height = 3, bd = 0, bg = "#fff", cursor = "hand2", command = lambda: btn_click(1)).grid(row = 3, column = 0, padx = 1, pady = 1)
 
two = Button(btns_frame, text = "2", fg = "black", width = 10, height = 3, bd = 0, bg = "#fff", cursor = "hand2", command = lambda: btn_click(2)).grid(row = 3, column = 1, padx = 1, pady = 1)
 
three = Button(btns_frame, text = "3", fg = "black", width = 10, height = 3, bd = 0, bg = "#fff", cursor = "hand2", command = lambda: btn_click(3)).grid(row = 3, column = 2, padx = 1, pady = 1)
 
plus = Button(btns_frame, text = "+", fg = "black", width = 10, height = 3, bd = 0, bg = "#eee", cursor = "hand2", command = lambda: btn_click("+")).grid(row = 3, column = 3, padx = 1, pady = 1)
 
# fourth row
 
zero = Button(btns_frame, text = "0", fg = "black", width = 21, height = 3, bd = 0, bg = "#fff", cursor = "hand2", command = lambda: btn_click(0)).grid(row = 4, column = 0, columnspan = 2, padx = 1, pady = 1)
 
point = Button(btns_frame, text = ".", fg = "black", width = 10, height = 3, bd = 0, bg = "#eee", cursor = "hand2", command = lambda: btn_click(".")).grid(row = 4, column = 2, padx = 1, pady = 1)
 
equals = Button(btns_frame, text = "=", fg = "black", width = 10, height = 3, bd = 0, bg = "#eee", cursor = "hand2", command = lambda: bt_equal()).grid(row = 4, column = 3, padx = 1, pady = 1)
 
win.mainloop()

There are a variety of functions in Tkinter with the help of them it becomes easy and convenient to make a simple calculator just with this little code.

Now we will show you a snapshot as the output of the above code. And yes you can implement it on your system for more clear understanding of Calculator App Using Tkinter:


calculator app example with tkinter

Summary:

In this tutorial, we developed a basic Calculator application using Tkinter and various widgets of Tkinter about which we have covered in our Tkinter Tutorial. Click on Next to see more Apps developed using Tkinter as this will help you practice what you have learned.