Create a Calculator in Python

In this example, we will show you how to to create a GUI calculator using the tkinter standard GUI library of Python.

The calculator should look like this:

Create Calculator in Python

The following code creates and displays a calculator in Python:


# importing required libraries
import tkinter
from tkinter import *
from tkinter import messagebox

# setting initial values of some variables
var = ""
A = 0
operator = ""

# defining function for Button 1
def button_1_is_Clicked():
    global var
    var = var + "1"
    _data.set(var)

# defining function for Button 2
def button_2_is_Clicked():
    global var
    var = var + "2"
    _data.set(var)

# defining function for Button 3
def button_3_is_Clicked():
    global var
    var = var + "3"
    _data.set(var)

# defining function for Button 4
def button_4_is_Clicked():
    global var
    var = var + "4"
    _data.set(var)

# defining function for Button 5
def button_5_is_Clicked():
    global var
    var = var + "5"
    _data.set(var)

# defining function for Button 6
def button_6_is_Clicked():
    global var
    var = var + "6"
    _data.set(var)

# defining function for Button 7
def button_7_is_Clicked():
    global var
    var = var + "7"
    _data.set(var)

# defining function for Button 8
def button_8_is_Clicked():
    global var
    var = var + "8"
    _data.set(var)

# defining function for Button 9
def button_9_is_Clicked():
    global var
    var = var + "9"
    _data.set(var)

# defining function for Button 0
def button_0_is_Clicked():
    global var
    var = var + "0"
    _data.set(var)

# defining function for Button +
def button_Add_is_Clicked():
    global A
    global var
    global operator
    A = float(var)
    operator = "+"
    var = var + "+"
    _data.set(var)

# defining function for Button -
def button_Sub_is_Clicked():
    global A
    global var
    global operator
    A = float(var)
    operator = "-"
    var = var + "-"
    _data.set(var)

# defining function for Button *
def button_Mul_is_Clicked():
    global A
    global var
    global operator
    A = float(var)
    operator = "*"
    var = var + "*"
    _data.set(var)

# defining function for Button /
def button_Div_is_Clicked():
    global A
    global var
    global operator
    A = float(var)
    operator = "/"
    var = var + "/"
    _data.set(var)

# defining function for Button =
def button_Equal_is_Clicked():
    global A
    global var
    global operator
    A = float(var)
    operator = "="
    var = var + "="
    _data.set(var)

# defining function for Button C
def button_C_is_Clicked():
    global A
    global var
    global operator
    var = ""
    A = 0
    operator = ""
    _data.set(var)

# defining function to display result
def res():
    global A
    global operator
    global var
    var2 = var
    if operator == "+":
        a = float((var2.split("+")[1]))
        x = A + a
        _data.set(x)
        var = str(x)
    elif operator == "-":
        a = float((var2.split("-")[1]))
        x = A - a
        _data.set(x)
        var = str(x)
    elif operator == "*":
        a = float((var2.split("*")[1]))
        x = A * a
        _data.set(x)
        var = str(x)
    elif operator == "/":
        a = float((var2.split("/")[1]))
        if a == 0:
            messagebox.showerror("Division by 0 Not Allowed.")
            A == ""
            var = ""
            _data.set(var)
        else:
            x = float(A/a)
            _data.set(x)
            var = str(x)


# creating an object of  Tk() class
guiWindow = tkinter.Tk()
# setting size of  window
guiWindow.geometry("320x500+300+300")
# disabling resize option
guiWindow.resizable(0, 0)
# setting title of window
guiWindow.title("GUI Calculator")

# creating calculator display screen
_data = StringVar()
guiLabel = Label(
    guiWindow,
    text="Label",
    anchor=SE,
    font=("Cambria Math", 30),
    textvariable=_data,
    background="#ffffff",
    fg="#000000"
)
# using pack() method
guiLabel.pack(expand=True, fill="both")

# creating frames for  buttons
# first frame
frameOne = Frame(guiWindow, bg="#000000")
# frame can expand if it gets some space
frameOne.pack(expand=True, fill="both")

# second frame
frameTwo = Frame(guiWindow, bg="#000000")
frameTwo.pack(expand=True, fill="both")

# third frame
frameThree = Frame(guiWindow, bg="#000000")
frameThree.pack(expand=True, fill="both")

# fourth frame
frameFour = Frame(guiWindow, bg="#000000")
frameFour.pack(expand=True, fill="both")

# creating buttons for each frame
# buttons for first frame
# button 1
buttonONE = Button(
    frameOne,
    text="1",
    font=("Cambria", 22),
    relief=GROOVE,
    border=0,
    command=button_1_is_Clicked
)
# placing buttons side by side
buttonONE.pack(side=LEFT, expand=True, fill="both")

# button 2
buttonTWO = Button(
    frameOne,
    text="2",
    font=("Cambria", 22),
    relief=GROOVE,
    border=0,
    command=button_2_is_Clicked
)
# placing buttons side by side
buttonTWO.pack(side=LEFT, expand=True, fill="both")

# button 3
buttonTHREE = Button(
    frameOne,
    text="3",
    font=("Cambria", 22),
    relief=GROOVE,
    border=0,
    command=button_3_is_Clicked
)
# placing buttons side by side
buttonTHREE.pack(side=LEFT, expand=True, fill="both")

# button C
buttonC = Button(
    frameOne,
    text="C",
    font=("Cambria", 22),
    relief=GROOVE,
    border=0,
    command=button_C_is_Clicked
)
# placing buttons side by side
buttonC.pack(side=LEFT, expand=True, fill="both")

# buttons for second frame
# button 4
buttonFOUR = Button(
    frameTwo,
    text="4",
    font=("Cambria", 22),
    relief=GROOVE,
    border=0,
    command=button_4_is_Clicked
)
# placing buttons side by side
buttonFOUR.pack(side=LEFT, expand=True, fill="both")

# button 5
buttonFIVE = Button(
    frameTwo,
    text="5",
    font=("Cambria", 22),
    relief=GROOVE,
    border=0,
    command=button_5_is_Clicked
)
# placing buttons side by side
buttonFIVE.pack(side=LEFT, expand=True, fill="both")

# button 6
buttonSIX = Button(
    frameTwo,
    text="6",
    font=("Cambria", 22),
    relief=GROOVE,
    border=0,
    command=button_6_is_Clicked
)
# placing buttons side by side
buttonSIX.pack(side=LEFT, expand=True, fill="both")

# button +
buttonADD = Button(
    frameTwo,
    text="+",
    font=("Cambria", 22),
    relief=GROOVE,
    border=0,
    command=button_Add_is_Clicked
)
# placing buttons side by side
buttonADD.pack(side=LEFT, expand=True, fill="both")

# buttons for third frame
# button 7
buttonSEVEN = Button(
    frameThree,
    text="7",
    font=("Cambria", 22),
    relief=GROOVE,
    border=0,
    command=button_7_is_Clicked
)
# placing buttons side by side
buttonSEVEN.pack(side=LEFT, expand=True, fill="both")

# button 8
btnEIGHT = Button(
    frameThree,
    text="8",
    font=("Cambria", 22),
    relief=GROOVE,
    border=0,
    command=button_8_is_Clicked
)
# placing buttons side by side
btnEIGHT.pack(side=LEFT, expand=True, fill="both")

# button 9
buttonNINE = Button(
    frameThree,
    text="9",
    font=("Cambria", 22),
    relief=GROOVE,
    border=0,
    command=button_9_is_Clicked
)
# placing buttons side by side
buttonNINE.pack(side=LEFT, expand=True, fill="both")

# button -
buttonSUB = Button(
    frameThree,
    text="-",
    font=("Cambria", 22),
    relief=GROOVE,
    border=0,
    command=button_Sub_is_Clicked
)
# placing buttons side by side
buttonSUB.pack(side=LEFT, expand=True, fill="both")

# buttons for fourth frame
# button 0
buttonZERO = Button(
    frameFour,
    text="0",
    font=("Cambria", 22),
    relief=GROOVE,
    border=0,
    command=button_0_is_Clicked
)
# placing buttons side by side
buttonZERO.pack(side=LEFT, expand=True, fill="both")

# button *
buttonMUL = Button(
    frameFour,
    text="*",
    font=("Cambria", 22),
    relief=GROOVE,
    border=0,
    command=button_Mul_is_Clicked
)
# placing buttons side by side
buttonMUL.pack(side=LEFT, expand=True, fill="both")

# button /
buttonDIV = Button(
    frameFour,
    text="/",
    font=("Cambria", 22),
    relief=GROOVE,
    border=0,
    command=button_Div_is_Clicked
)
# placing buttons side by side
buttonDIV.pack(side=LEFT, expand=True, fill="both")

# button +
btnEQUAL = Button(
    frameFour,
    text="=",
    font=("Cambria", 22),
    relief=GROOVE,
    border=0,
    command=res
)
# placing buttons side by side
btnEQUAL.pack(side=LEFT, expand=True, fill="both")

# running  GUI
guiWindow.mainloop()


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