Home ยป A Simple calculator using Tkinter and Python

# A Simple calculator using Tkinter and Python

In this example we will create a GUI-based simple calculator using Tkinter, this simple calculator will be able to perform basic arithmetic operations addition, subtraction, multiplication, and division.

### Code

Most of the code is to draw the buttons in the GUI

```from tkinter import *

expression = ""

# Function to update text entry box
def press(num):
global expression
expression = expression + str(num)
equation.set(expression)

# Function to evaluate the final expression
def equalpress():
try:

global expression
# evaluate the expression
total = str(eval(expression))
equation.set(total)
expression = ""

# error handling
except:
equation.set(" error ")
expression = ""

# Function to clear the contents
# of text entry box
def clear():
global expression
expression = ""
equation.set("")

# Driver code
if __name__ == "__main__":
# create a GUI window
gui = Tk()

# background colour of GUI window
gui.configure(background="light blue")

# title of GUI window
gui.title("Calculator")

# GUI window
gui.geometry("270x150")
equation = StringVar()

# create the text entry box for
# showing the expression .
expression_field = Entry(gui, textvariable=equation)

# grid

# create Buttons.
button1 = Button(gui, text=' 1 ', fg='black', bg='red', command=lambda: press(1), height=1, width=7)
button1.grid(row=2, column=0)

button2 = Button(gui, text=' 2 ', fg='black', bg='red', command=lambda: press(2), height=1, width=7)
button2.grid(row=2, column=1)

button3 = Button(gui, text=' 3 ', fg='black', bg='red', command=lambda: press(3), height=1, width=7)
button3.grid(row=2, column=2)

button4 = Button(gui, text=' 4 ', fg='black', bg='red', command=lambda: press(4), height=1, width=7)
button4.grid(row=3, column=0)

button5 = Button(gui, text=' 5 ', fg='black', bg='red', command=lambda: press(5), height=1, width=7)
button5.grid(row=3, column=1)

button6 = Button(gui, text=' 6 ', fg='black', bg='red', command=lambda: press(6), height=1, width=7)
button6.grid(row=3, column=2)

button7 = Button(gui, text=' 7 ', fg='black', bg='red', command=lambda: press(7), height=1, width=7)
button7.grid(row=4, column=0)

button8 = Button(gui, text=' 8 ', fg='black', bg='red', command=lambda: press(8), height=1, width=7)
button8.grid(row=4, column=1)

button9 = Button(gui, text=' 9 ', fg='black', bg='red', command=lambda: press(9), height=1, width=7)
button9.grid(row=4, column=2)

button0 = Button(gui, text=' 0 ', fg='black', bg='red', command=lambda: press(0), height=1, width=7)
button0.grid(row=5, column=0)

plus = Button(gui, text=' + ', fg='black', bg='red', command=lambda: press("+"), height=1, width=7)
plus.grid(row=2, column=3)

minus = Button(gui, text=' - ', fg='black', bg='red', command=lambda: press("-"), height=1, width=7)
minus.grid(row=3, column=3)

multiply = Button(gui, text=' * ', fg='black', bg='red', command=lambda: press("*"), height=1, width=7)
multiply.grid(row=4, column=3)

divide = Button(gui, text=' / ', fg='black', bg='red', command=lambda: press("/"), height=1, width=7)
divide.grid(row=5, column=3)

equal = Button(gui, text=' = ', fg='black', bg='red', command=equalpress, height=1, width=7)
equal.grid(row=5, column=2)

clear = Button(gui, text='Clear', fg='black', bg='red', command=clear, height=1, width=7)
clear.grid(row=5, column='1')

Decimal= Button(gui, text='.', fg='black', bg='red', command=lambda: press('.'), height=1, width=7)
Decimal.grid(row=6, column=0)
# start the GUI
gui.mainloop()```

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