Welcome folks today in this blog post we will be building a mini calculator in tkinter using python. All the full source code of the application will be given below.

Get Started

In order to get started make an app.py file and copy paste the following code

app.py

# importing Tkinter and math 
from tkinter import *
import math 

# calc class 
class calc: 

    def getandreplace(self): 

        """replace x with * and � with /"""
        self.expression = self.e.get() 
        self.newtext=self.expression.replace('/','/') 
        self.newtext=self.newtext.replace('x','*') 


    def equals(self): 
        """when the equal button is pressed"""
        self.getandreplace() 
        try: 
            # evaluate the expression using the eval function 
            self.value= eval(self.newtext) 
        except SyntaxError or NameError: 
            self.e.delete(0,END) 
            self.e.insert(0,'Invalid Input!') 
        else: 
            self.e.delete(0,END) 
            self.e.insert(0,self.value) 

    def squareroot(self): 
        """squareroot method"""
        self.getandreplace() 
        try: 
            # evaluate the expression using the eval function 
            self.value= eval(self.newtext) 
        except SyntaxError or NameError: 
            self.e.delete(0,END) 
            self.e.insert(0,'Invalid Input!') 
        else: 
            self.sqrtval=math.sqrt(self.value) 
            self.e.delete(0,END) 
            self.e.insert(0,self.sqrtval) 

    def square(self): 
        """square method"""
        self.getandreplace() 
        try: 
            #evaluate the expression using the eval function 
            self.value= eval(self.newtext) 
        except SyntaxError or NameError: 
            self.e.delete(0,END) 
            self.e.insert(0,'Invalid Input!') 
        else: 
            self.sqval=math.pow(self.value,2) 
            self.e.delete(0,END) 
            self.e.insert(0,self.sqval) 

    def clearall(self): 
            """when clear button is pressed,clears the text input area"""
            self.e.delete(0,END) 

    def clear1(self): 
            self.txt=self.e.get()[:-1] 
            self.e.delete(0,END) 
            self.e.insert(0,self.txt) 

    def action(self,argi): 
            """pressed button's value is inserted into the end of the text area"""
            self.e.insert(END,argi) 

    def __init__(self,master): 
            """Constructor method"""
            master.title('Calulator') 
            master.geometry() 
            self.e = Entry(master) 
            self.e.grid(row=0,column=0,columnspan=6,pady=3) 
            self.e.focus_set() #Sets focus on the input text area 

            # Generating Buttons 
            Button(master,text="=",width=11,height=3,fg="blue", 
                bg="orange",command=lambda:self.equals()).grid( 
                                    row=4, column=4,columnspan=2) 

            Button(master,text='AC',width=5,height=3, 
                        fg="red", bg="light green", 
            command=lambda:self.clearall()).grid(row=1, column=4) 

            Button(master,text='C',width=5,height=3, 
                fg="red",bg="light green", 
                command=lambda:self.clear1()).grid(row=1, column=5) 

            Button(master,text="+",width=5,height=3, 
                fg="blue",bg="orange", 
                command=lambda:self.action('+')).grid(row=4, column=3) 

            Button(master,text="x",width=5,height=3, 
                    fg="blue",bg="orange", 
                    command=lambda:self.action('x')).grid(row=2, column=3) 

            Button(master,text="-",width=5,height=3, 
                    fg="red",bg="light green", 
                    command=lambda:self.action('-')).grid(row=3, column=3) 

            Button(master,text="�",width=5,height=3, 
                fg="blue",bg="orange", 
                command=lambda:self.action('/')).grid(row=1, column=3) 

            Button(master,text="%",width=5,height=3, 
                fg="red",bg="light green", 
                command=lambda:self.action('%')).grid(row=4, column=2) 

            Button(master,text="7",width=5,height=3, 
                fg="blue",bg="orange", 
                command=lambda:self.action('7')).grid(row=1, column=0) 

            Button(master,text="8",width=5,height=3, 
                fg="red",bg="light green", 
                command=lambda:self.action(8)).grid(row=1, column=1) 

            Button(master,text="9",width=5,height=3, 
                fg="blue",bg="orange", 
                command=lambda:self.action(9)).grid(row=1, column=2) 

            Button(master,text="4",width=5,height=3, 
                fg="red",bg="light green", 
                command=lambda:self.action(4)).grid(row=2, column=0) 

            Button(master,text="5",width=5,height=3, 
                fg="blue",bg="orange", 
                command=lambda:self.action(5)).grid(row=2, column=1) 

            Button(master,text="6",width=5,height=3, 
                fg="white",bg="blue", 
                command=lambda:self.action(6)).grid(row=2, column=2) 

            Button(master,text="1",width=5,height=3, 
                fg="red",bg="light green", 
                command=lambda:self.action(1)).grid(row=3, column=0) 

            Button(master,text="2",width=5,height=3, 
                fg="blue",bg="orange", 
                command=lambda:self.action(2)).grid(row=3, column=1) 

            Button(master,text="3",width=5,height=3, 
                fg="white",bg="blue", 
                command=lambda:self.action(3)).grid(row=3, column=2) 

            Button(master,text="0",width=5,height=3, 
                fg="white",bg="blue", 
                command=lambda:self.action(0)).grid(row=4, column=0) 

            Button(master,text=".",width=5,height=3, 
                fg="red",bg="light green", 
                command=lambda:self.action('.')).grid(row=4, column=1) 

            Button(master,text="(",width=5,height=3, 
                fg="white",bg="blue", 
                command=lambda:self.action('(')).grid(row=2, column=4) 

            Button(master,text=")",width=5,height=3, 
                fg="blue",bg="orange", 
                command=lambda:self.action(')')).grid(row=2, column=5) 

            Button(master,text="?",width=5,height=3, 
                fg="red",bg="light green", 
                command=lambda:self.squareroot()).grid(row=3, column=4) 

            Button(master,text="x�",width=5,height=3, 
                fg="white",bg="blue", 
                command=lambda:self.square()).grid(row=3, column=5) 

# Driver Code 
root = Tk() 

obj=calc(root) # object instantiated 

root.mainloop()

Now if you execute the python script app.py by typing the below command as shown below

python app.py