Calculator Application Using Python Language

The Calculator is one application that we all utilize in our day-to-day lives. If you are attempting to get your hands dirty with programming in python, Calculator is a straightforward and helpful project at the same time. Today, we will develop a Python Calculator using Tkinter with simple to follow instructions.

Here is how our calculator will appear, which is created using the input field, buttons, and logic defined in functions for calculation purposes. For example, if you want to add two numbers, there must be logic for addition, similarly for subtraction, multiplication, and so on, we have created functions whose task is to perform these operations.

We have an Input Field where the user input will be shown along with the calculation's ultimate result.

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

What is a Calculator?

For those unfamiliar, a calculator is a computer application that mimics the behaviour of any hand-held calculator used for completing mathematical calculations. It is a really simple item that we use on a daily basis. A Calculator application is now available on all cellphones.

There are primarily two processes involved in developing any GUI application:

• Creating a User Interface is the initial stage.
• The second and most crucial stage is to provide the functionality to the graphical user interface.

Let's get started by making a simple calculator app in Python utilizing Tkinter for basic arithmetic calculations.

Source Code for Calculator Application

Now it's time to look at the code for making a Tkinter Calculator App:

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 enter 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()

Tkinter has a number of methods that make it simple and quick to create a basic calculator with only a few lines of code.

We've defined the following functions in our code, in addition to the Tkinter widgets:

• btn click() Function: This function adds various numeric buttons to the operation by handling button clicks.
• The bt clear() method is used to handle the clear action in the Calculator application, which cleans the previous input.

The equal button is handled by the bt equal() function, which does the action and displays the result.

Now we'll show you a screenshot of the aforementioned code's result. Yes, you may use it on your machine to have a better knowledge of Calculator App Using Tkinter:

Output:

Summary:

In this article, we used Tkinter and several Tkinter widgets to create a simple Calculator application, which we covered in our Tkinter Tutorial.